After reading a little about using filters to cut down RGB levles when calibrating which maintains contrast ratio as apposed to cutting the levels digitally I thought I'd give it a try. I went on the cheap and purchased square glass filters from Cokin which were half price at the local shop, the filters slide into a housing therefore they can be stacked if neccessary. Taking a look at the relative RGB levels when using the projectors High temp and very blue mode it was clear substantial cuts in blue and green were required but not equally. I needed to bring blue down more than green in about a 1:3 ratio to get the two to match.

Orange filters absorb blue and green with the emphasis on blue so felt orange may be a perfect match but this still left how much total absorbtion required to bring the levels down to red. The outlet I was at only had one orange filter so the decision was easy and as it turns out was a little too aggressive therefore it was required to bring red down to match to new levels of blue/green so some lumens were needlessly lost but that's ok in my system as the screen way too bright anyway. As you can see from the new RGB histogram with the filter installed using the pj's high temp with all RGB levels at default maxed out positions I think I got pretty lucky. Don't think I could ask for a better result from a $15 filter with respect to bringing down blue and green.

During my readings I came across posts which indicated that while the filters may increase or actually maintain contrast there could be a hit in the representation of the colors.

So the big question, how much potential does this filter tweak have for increasing contrast ratio over calibrating only digitally. I don't have a dedicated light meter but am using an Eyeone Display sensor through HCFRcolorimater software. The sensor is placed on a tripod about 18 inches from the lens of the PJ to bring up black levels the meter can comfortably measure. I measured the CR for the PJ with 100% white calibrated to .2 dE from D65 using the RGB controls only plus another CR measurement using the native High Temp with the orange filter in place, 100% white then further digitally adjusted to within .3 dE from D65. My result are:

No filter D65 CR: 14038
D65/filter Hi CR: 17016
Hi temp default: 17125

You need to measure Luv (xyY) of color - not just uv (xy). Is that pre/post filter gamut or a reference gamut vs. post filter? Does your software have dE targets for color? The CIE gamut chart is poor for visualizing color error difference as it covers the entire color space which is several hundred dE wide. You can see as small as a 3dE difference - which is not going to show on a gamut chart. This is evident in your greyscale appearing to be on target on the gamut chart - but clearly is 10-20dE off on the dE chart.

Here are charts of an FL-D filter on a SP7210 - in these older charts I was not measuring L for color as I do now - but you can see the impact on delC (chroma) and delH (hue). Basically what these charts say is the WMYR gamut got more red. These older charts do not record contrast/lumens - but if I recall it was something like 30% more contrast for 15% less lumens - and if I used white peaking and abused the gamma curve it was a 100% boost to contrast.

http://krasmuzik.biz/reviews/SP7210.pdf

Your max potential would be whatever contrast ratio it has at it's native maxed out color temp - presuming you find the filter that optically calibrates it.

Hello Krasmuzik,

The gamut is post filter, they grayscale off due to there being some ambient light in the room therefore I spent no time on the entire grayscale, I made note of it somewhere in my OP. I'll be spending more time on it later tonight.

My software does provide color dE but alone probably won't mean a whole lot. I didn't run a reference measure without filter, the reference I have was performed last week but plan on running the entire series of measurements again tonight for so the two can be compared. I have the xyY values but will post them with dE from the measrements taken tonight.

I'm not quite at the max potential due the requirement to pull red down digitally quite a bit but am reasonably close. I measured CR at high temp last week in the mid 18's, but again that was another measurement session with a different set of variables ie: pitch black room.

You have to admit though the filter I picked was a stroke of good luck. :D

Appreciate further input when I get a full set of measrements.

Yes dE for color is not the whole story - but an overall error - be it hue, chroma or lightness. I use LCH for charting - but use dE (RMS) for overall grading. LCH is perceptually weighted so that the error units are balanced in each of the LCH dimensions.

Krasmuzik,

What are the dE ring values in your posted charts. Now I see what you mean regarding screwing the colors.

10dE, 30dE, 50dE...I had to standardize on 60dE as my chart limit - indeed I have measured some that go beyond that limit, but any further you lose the detail around the bulls eye!

dE is actually a sphere not a ring - but too confusing to represent errors in 3D - so the gamma deviation for greyscale and color lightness errors is charted seperately.

On my website I describe the charts - I convert dE (RMS) to percent by subtracting from 100 to assign grades. So roughly the rings are excellent, adequate or very poor.

http://www.krasmuzik.biz/reviews/reviewformat.htm

FYI this chart format is Copyright KRAS Muzik, LLC 2005-2007.

The colorspaces used however are CIE 1976 standard - so anyone is free to generate the numbers - I just do not want to see my chart format showing up in calibration software.


In this SP7210 example the tint control cannot fix the problem - the FL-D does not affect the Cyan hue while it pushes the Yellow and Magneta tints towards red (+delH is counterclockwise hue error, -delH is clockwise hue error). Only a proper CMS can fix that - which Infocus does not have. Be interesting to plot these charts showing color/tint control extremes - maybe next time I calibrate.

Hugh,

That's a nice 20% increase in CR. How visible is it with program material, and especially, blackouts?

Noah,

Too early to tell, I'll be viewing tonight with a black room. In theory this tweak should cure the bright corners somewhat by reducing ultimate black levels thereby lowering our sensitivity and also I believe that the bright corners is native blue heavy light leaking through therefore the filter should also reduce this blue excess of the native lamp color shining through again making the corners less visible if not invisible.

Did this Orange filter tame the neon oversaturated greens ?

I've updated my first post with a new set of contrast ratios which are very close to what I measured earlier but now included is the CR at High Temp full output. Regarding full output at high temp, I found that with both sets of RGB adjustments at default 0 the panels were not fully driven, the offset controls allow levels to be increased to which I set both green and blue and +6 before the onset of clipping.

Attempting to calibrate with the filter in place has proved a little frustrating. For some reason there's a bit of a seesaw effect to reds response the fulcrum about in the middle of the grayscale. The best I could do provides a dE error at 20% of about 7.5 and 3.9 at 100%, the middle grays all approach dE of .75. Calibrating without the filter provides much more linear dE of under 1 until about 30% at which point blue takes off providing dE of 12 and more at 20% and lower. Not a big deal but the dark grays start out warm and get cooler the closer to 100% you get.

The filter has increased gamma slighly to an average of 2.24, the highest I could muster without crushing blacks sans filter was 1.15. there is a slight anomaly here though, with filter in place green and blue track together at above 2.24 red has taken it's own course however at a lower gamma of about 2.18.

Regarding color, here's the before and after xyY numbers for primaries and secondaries. I'll also include the dE as laid out in the CIEu'v' chart. Forget it I can't seem to do a list that is legible, if someone could provide instruction for lists I'd appreciate it. For now here's the dE numbers for rec709 standard. Keep in mind the dE are high do to the JVC's large color Gamut.

....N/F..Filter
R 19.5 21.5
G 38.0 34.6
B 45.9 41.5
Y 20.7 21.1
C 19.4 17.5
M 15.9 18.4

No filter average dE: 25.567, with filter average dE: 25.767.

So to sum up thus far effects of using this filter:

1- increased contrast ratio of 21% from 14038 to 17016

2- Decrease in light output of about 25%, this filter is more aggressive than required but works wonders in my too bright setup.

3- Significant decrease in bright corner issue, one of my corners actually took up about 1/5 of the screen. Not only has the perceived area been reduced to about half that the color of remaining area is less offensive.

So far so good.

Did this Orange filter tame the neon oversaturated greens ?

Green moved slightly, but am not sure how noticeable it is. I'm not too sure that the neon and oversaturion are the same issue. Oversaturation would make the colors deeper in color, the neon or glowing issue seems more of an color intensity of brightness issue. Maybe they go hand in hand but I'm not entirely convinced as yet.

Your GCB gamut has less error - your CYR gamut has more error- this is why your average did not change much - so it has a tradeoff really since it is just a shift in balance for the color errors.

The color intensities must be way off from color decoder requirements - as your Blue did not look that far off on the gamut chart like Green is. Possible your sensor is just not good at reading dark blues...did you get as close to lens as possible to increase light output?

Be interesting to break down the xyY raw data to LCH color space and see what the errors are - but I don't know how to post a list either! Maybe attach an Excel file? Since LCH can all be over/under target- you get a better picture looking at it. Does dL, dC, dH each shift from +20 to -20 for no net dE change - but a large perceptual change?

I'm looking for a colorspace converter, found one but it's not performing the said tasks, I'll keep working on it. I can't even post an excel, recently upgraded my computers and they don't even have the basic work spreadsheet on them anymore, what a rip!

I only got close to the lens when measuring contrast ratio, all other measurements the meter faced the HP screen. I've performed dozens of measures and the results of blue are always consistant which provides me some faith it's capable of, at the very, reading the light level. I've noticed anything about 1 cd/m2 the cut-off for faithfull repeatability, the 75% blues always fall above that. Full resolution CIE charts show the errors between red green and blue about equal visually, I suppose if the filter is moving the primaries non-relative to each other this may be causing the error in secondaries as it's not as JVC intended. Since the JVC does not have a blue screen mode I'm using filters to adjust the color decoder which as you is not the most accurate method but all three colors (utilizing the squint method) look bang on, better than I've ever witnessed.

I'll do my best to covert xyY to LCH but not right now, all this typing is cutting into my drinking time and that's something I'll never get back.

Just realized I haven't provided any info on the filter. It is a Cokin P029 85A Color Conversion Resin Filter. Here's a photo of the filter in the separate housing.

So to sum up thus far effects of using this filter:

1- increased contrast ratio of 21% from 14038 to 17016

2- Decrease in light output of about 25%, this filter is more aggressive than required but works wonders in my too bright setup.

3- Significant decrease in bright corner issue, one of my corners actually took up about 1/5 of the screen. Not only has the perceived area been reduced to about half that the color of remaining area is less offensive.

So far so good.

Thanks this is very informative. Can you take a before/after shot of your CIE chart? Have you measured ANSI CR before/after? Word is that CCF filters may have an adverse affect on ANSI CR so it would be useful to know if that applied in this case. Lastly, can you discern a difference that the 21% increase in on/off CR makes?

Kras,

I found a conversion calculator which converted my xyY values to LCHuv: But at this point can not find the standards for LCH?? Here's a "list" of numbers

________ L__________C_________H

NO FILTER

R ____ 45.033943 158.863377 13.149837
G____ 55.213175 106.808380 128.961929
B____ 21.341089 93.334756 264.908006
Y____ 71.084812 92.959002 78.415043
C____ 61.953332 65.682267 208.892535
M____ 49.453629 113.891737 311.832498

FILTER

R ____ 34.703447 122.402773 13.011432
G____ 55.056884 104.487092 128.029202
B____ 16.815835 73.543663 264.908006
Y____ 62.418050 81.711387 85.416330
C____ 58.01901 56.013365 188.930635
M____ 38.669600 93.224710 306.413141


The changes in Lightness, Chroma, and Hue are rather interestng. Can you steer me towards the standards and perhaps a Delta calculator. I can do the calcs using LAB but not for LCH. An obvious question, where chroma is >100 and the model for chroma is 0-100 is the LCH chroma space smaller than CIE space.

Here's a link to the Bruce Lindbloom converter I used:
http://brucelindbloom.com/index.html?ColorCalcHelp.html

Here are the xyY coordinates

Filtered

R...660....336...8.351
G...293....704..22.137
B...139....049...2.264
Y...448....550...30.894
C...206....336...25.981
M...317....146...10.468

100% white Y 46.826

No Filter

R...661....337...14.566
G...286...712....23.137
B...139....049....3.357
Y...463....535...42.311
C...193....291...30.348
M...334....158...17.965

100% white Y 61.782

Rec.709 standard (Tom, I stole this from your post)

Rec. 709-------x-------y-------Y
R--------------0.640---0.330---0.213
G--------------0.300---0.600---0.715
B--------------0.150---0.060---0.072
C--------------0.225---0.329---0.787
Y--------------0.419---0.505---0.928
M--------------0.321---0.154---0.285
White----------0.313---0.329---1

If I'm reading this correctly then based on the filtered results I should be cranking up the color brightness control?? Using DVE's RGB filters the color brightness appear almost perfect.

Hugh,
Is that a Cokin plastic filter?????????, are you getting any distortion from the heat on the plastic ??????????? How far are you in front of the lense????????? I thought about using a ND filter, buts its glass.
Thanks

Hugh,
Is that a Cokin plastic filter?????????, are you getting any distortion from the heat on the plastic ??????????? How far are you in front of the lense????????? I thought about using a ND filter, buts its glass.
Thanks

It's labelled as resin, feels just like glass. The filter is about 3/4 inch in front of the lens with no heat issues.

Ok, some more numbers to look at. I located a Delta E calculator for LAB colorspace which appears to resemble closely LCH so I converted all my xyY measurements to LAB. I then calculated a different reference set of values for the non-fltered and filtered setup using the luminance value of each.

Here's the calculator:
http://www.colorspan.com/support/tools/deltae.asp

Here's the Delta E chart:

............Filtered.........Non-filtered
R.............7.34..............19.58
G...........31.2...............77.43
B.............4.72...............6.24
Y...........31.18.............41.68
C...........11.5...............17.99
M............4.93................3.67

Ave.......15.145...........27.765

You may notice some more lens flare and reduced ANSI with the resin filters. I would try a HMC Hoya equivalent as they have less effect on the image compared to the Cokin ones. I noticed that when I tried a Cokin FL-D filter so for long term use I now use Hoya.

Gary

Hello,

I just picked up something very inexpensive for an experiment. I''ve been enjoying the improvement, mainly in reduced foot Lamberts and better blacks, but I've have yet to notice any negatives with the filter. I plan on purchasing the two lighter versions of this Cokin, if I can get the brigtness just right I'll not even need to adjust the red more than a few clicks plus I can throw those on to compensate for lamp brigtness loss if desired.

Beyond measurement, have you noticed any changes in hue? Often your reds will look orangey with an 85 series filter.

BTW, here's a chart of how the 85 series filters affect the spectrum.

I haven't noticed any shift of red hue to orange, if anything it appears deeper red but this I'm sure just a product of reduced brightness. I really can't see any negatives being introduced by using this filter yet. As time progresses that's likely to change, overall the picture is stunning but it was kinda like that before just a little too bright.

Thanks this is very informative. Can you take a before/after shot of your CIE chart? Have you measured ANSI CR before/after? Word is that CCF filters may have an adverse affect on ANSI CR so it would be useful to know if that applied in this case. Lastly, can you discern a difference that the 21% increase in on/off CR makes?

The CIE chart is esentially in number form a few posts up, it's easier to discern differences this way. I have not measured ANSI CR but I definitely don't perceive any drop and contrarily the perception is an improvement.

It's difficult to say if I can perceive the additional CR, the increased CR is accompanied by lower foot lamberts on the screen and both give the same perceived end result. As average scene brightness increases my rooms ability to support either contrast ratio decreases or disappears and eye bias takes over. There is a definitely a new sense of palpability and depth to the picture which could be attributed to the increase in CR but there's so many variable it's difficult to attribute this solely to CR though I'd like to.

Hugh2

The color equations are documented on that site.

Did you normalize Y (L) to 100 for white with each measurement set - that is the only way you can compare - white is always LCH (100,0,0). I suspect since your dE is less with the filter - you are using the white without filter as your reference. You need the filtered dE based on white with the filter, likewise nonfiltered dE based on white without the filter.

And I would use lens readings - while you may have repeatability this could be the software doing some averaging - you want accuracy for these primary measures which means more light on the sensor. Or just size down to a 2' image on screen.

Your sensors absolute accuracy is not all that important - what matters is the relative accuracy so that the delta measures are meaningful. Unless you want to compare to the references rather than just w/w.o. filter.

LAB and LCH have the same dE - it is take the root of the sum of the squares of the three target differences for each color. Make sure you use LCH though and not LCh for that to work.

dC, dL, dH are just the difference from each other - or the reference target however you want to express it.

Looking at your data the Chroma of Red increases and Blue decreases while Green was same and the Hues of the secondaries are perceptually changed as well as their Chroma reduced. Chroma includes Lightness - so you have to look at that to figure is the color stronger because it is brighter or more saturated.
.
.
.

Never mind I will recomment once you have indicated the data is properly normalized - WTF this is more interesting than taxes - I'll spreadsheet your data for you.

I can't even post an excel, recently upgraded my computers and they don't even have the basic work spreadsheet on them anymore, what a rip!



Hugh,

Not sure from your post, but in case it might be helpful there is an open source office suite called Open Office.

You can download it here. (http://download.openoffice.org/)

I just played around a little, but it is free, seemed intuitive, and the non-computer geek I installed it has continued to use it, and exchange documents with users of MS Office, on a regular basis.

The tough part was figuring out which program was the spreadsheet, which was the word processor, etc.

Just a suggestion, i realize that it might not be feasible on a work computer administered by someone else, etc.

Doug

Hugh2

Did you normalize Y (L) to 100 for white with each measurement set - that is the only way you can compare - white is always LCH (100,0,0). I suspect since your dE is less with the filter - you are using the white without filter as your reference. You need the filtered dE based on white with the filter, likewise nonfiltered dE based on white without the filter. .

Yes, I normalized my reference to the Y of each measurement set. Didn't catch that little oversight till about half-way through my calculations though, but I did catch it.

And I would use lens readings - while you may have repeatability this could be the software doing some averaging - you want accuracy for these primary measures which means more light on the sensor. Or just size down to a 2' image on screen..

Your sensors absolute accuracy is not all that important - what matters is the relative accuracy so that the delta measures are meaningful. Unless you want to compare to the references rather than just w/w.o. filter.

With the meter facing the screen I get excellent repeatability even at 20% and moreso when measuring primaries so I sort of trust the results. I've read a few posts about meters accuracy vs amount of light though that I will heed your advice and get more into the meter to see if anything changes.

I'm not going to claim my measuring equipment is reference quality but overtime of using I do get a sense that it's at the very least consistant. Barring significant LAB dE differences when pointed towards the lens I'm pleased with the measured performance of the lens, and more importantly the image looks really big and juicy. :D

Looking at your data the Chroma of Red increases and Blue decreases while Green was same and the Hues of the secondaries are perceptually changed as well as their Chroma reduced. Chroma includes Lightness - so you have to look at that to figure is the color stronger because it is brighter or more saturated.
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.
.

Never mind I will recomment once you have indicated the data is properly normalized - WTF this is more interesting than taxes - I'll spreadsheet your data for you.

LOL, I've been procrastinating that all well. If it wasn't for procrastination nothing would get done. Thanks for the help.

Which spectrometer/colorimeter and software are you using? Also, how are you using the device? Tripod? How does the mount work, which one? How far away? Getting accurate readings is hard. I was just curious if you could do a quick summary of the basics? Whenever I see someone post numbers they got, they're different than the "professionals" and even other professionals, like Ekkehart. Thanks.

I'm using an Eyeone Display sensor with HCFRcolorimeter software. The sensor is tripod mounted, see picture of custom high tech mount device below. When measuring contrast I place the sensor between 1 and 1.5 feet from the PJ's lens with the diffusor attached. For screen measurements I've found for the HP screen it's best to bring the meter off the screen several feet and place the head at the same angle of reflection as the seating position.

How have any of my measurement differed?

Hugh,

Not sure from your post, but in case it might be helpful there is an open source office suite called Open Office.

You can download it here. (http://download.openoffice.org/)

I just played around a little, but it is free, seemed intuitive, and the non-computer geek I installed it has continued to use it, and exchange documents with users of MS Office, on a regular basis.

The tough part was figuring out which program was the spreadsheet, which was the word processor, etc.

Just a suggestion, i realize that it might not be feasible on a work computer administered by someone else, etc.

Doug

Can't thank-you enough for the link. I've been searching unsuccessfully for a high value option.

With the meter facing the screen I get excellent repeatability even at 20% and moreso when measuring primaries so I sort of trust the results.



But how does it perform at 7.2%? Because that is the HD spec brightness for blue - and why it is hard to measure.

Here is my spreadsheet, I also linked it from my review format page, and it has links to the textbook equations I used.

http://krasmuzik.biz/reviews/CIE%20calcs.xls

I use CIELUV for computing the delta error since it is intended for light color, CIELAB is intended for surface color. Also H (Hue error) differs from h (hue angle) so that it can be included in the dE term.

The pre filter data looks like you did not have color and tint set properly - as dL and dH are off - also I suspect you adusted color/tint post filter - so not sure you can conclude anything as far as the delta created by the filter.

Adjust color/tint/grayscale pre-filter - then only adjust greyscale post-filter leaving color/tint alone if you want to know only what the filter is doing.

Here is my spreadsheet, I also linked it from my review format page, and it has links to the textbook equations I used.

http://krasmuzik.biz/reviews/CIE%20calcs.xls

...The pre filter data looks like you did not have color and tint set properly - as dL and dH are off - also I suspect you adusted color/tint post filter - so not sure you can conclude anything as far as the delta created by the filter.

Adjust color/tint/grayscale pre-filter - then only adjust greyscale post-filter leaving color/tint alone if you want to know only what the filter is doing.

Thanks for inputting those numbers, that's one teriffic speadsheet and a nice little gift for all. Regarding color and tint, I have no way to adjust tint but color brightness was adjusted once with DVE during the first pre-filter cal and not touched again. Not sure what to make of it, I did check color brightness post filter and post measurements for curiousity and it appeared the exact same so I left it. I'll definitely being re-running the measurements facing the lens.

Thanks again.

@Hugh2

The orange fiter is a nice match even though it cuts a bit much blue.... Have you tested other filters ? What about FL-D?

I'm also in the search for a suitable filter, and my greyscale at high temp look almost the same as yours, except a bit less blue.

http://i176.photobucket.com/albums/w192/anbjornk/HD1RGBtracking_high.jpg

I'm still in the search for detailed filterspecs so that it's possible to find a perfect match.
A yellow filter would probably fit my projector.....

anbjornk,

The 85a was the first and only filter I tested. I did buy a yellow filter but it's unopened as it wasn't required. In your case perhaps a yellow would be suitable to pull down blue leaving green and red relatively unaffected and left for digital adjustment.

Thanks. You really went for the high tech solution mount!

All measurements in general. I've seen UMR's calibration calibration reports and for the same exact display, the CIE values are radically different for each customer. I don't understand why that would be if all are the same display model and size. Also, with lumen measurements: projector central, projector reviews and cine4home can all be different by over 100 lumens. When you're only dealing with about 600 lumens , thats a huge difference.

I love the mount, works on compression against soft polysomething pads which keeps the sensor firmly in place and it's very easy to remove the sensor to re-calibrate absolute black against a dark no light surface when you accidentally x out of the program.

I think it's pretty fair that all these guys can stay within that range, factoring in errors and or tolerances within, equipment, lamps, measurement methods, throw ranges, bias etc. that's quite tight.

If you can get hold of the swatch of different filters that Lee filters sometimes send out, you can try the filters that may work while having the software in continuous measure mode. Just watch the bars or whatever measures the RGBs and the filter that corrects them closer to optimal should be relatively quick to find. Once you have one (or a combination of two, lumens allowing), you can buy the actual filter knowing it's the right one..

Gary

Hello Kraz,

I had a chance to run a second set of measures this time with the sensor facing the projector lens.

The largest errors are with L but both about the same overall, chroma and hue errors still has the filtered light with a slight edge.

I had to save file as jpeg and keep it small so hid much of the conversion fields.

Much more consistent now! So if we look for any error differences more than 3 - this will be the perceptual changes.

Really no significant change in dL, primary chroma shifted a bit closer in, and cyan and magenta hues worse while yellow moved in closer. The yellow must have shifted from grayscale tweaks as you would think an orange filter makes it more orange not less orange!

Even though red may be oversaturated on a CIE 1931 gamut chart - because dL has it a bit weaker brightness - the color will appear less strong. Chroma is strength of color - a combination of saturation and lightness - which is how the eye perceives things.

To put things in perspective using my subjective grading of overall color - the filter makes the colors improve from "barely very good" to "very good" - with taming of greens at expense of magenta - so it is still a far cry from "excellence" or "perfection".



I linked the spreadsheet in the calibration forum sticky thread for posterity.

I'm loving this spreadsheet, gives excellent insight of what's going on. A worthy sticky indeed. Second time I've said this today, I can't thank you enough.

It makes more sense when graphed in my review format - but I am saving that MatLab code for myself :D

I have been beating the drum for CIELCH for a few years now - and it really does track perception especially with customers that are not calibrators. I have used it for just simple pre/post reports up to full blown PJ review. Of course annoyances and perceptions are entirely different things! I get annoyed if it is 1% off even if maybe that is not really perceivable :D

If you want to play with filters or controls CIELCH gives you better insight into the tradeoffs made - and as you do this on more displays you understand the tricks manufacturers play. The trick JVC played compared to Sony - the colors are not as brite as they could be which offsets the oversaturation - whereas the Sony makes the colors glow as well as being too deep.

I just realized why my L's were so low, I've reference my white point at 100% and am displaying full color fields at 75% duh! I ran the primaries again at 100% but don't have 100% secondary field yet. Things are now looking a little more normal, all L under dE 3 but the edge to filtered light. The filter chroma is obviously still way off, the edge to filtered light and all hues are under 3 dE again with the slight edge with filter. Look forward to completing this with secondaries but can't do anymore without the proper test dvd. :o

Sheepishly stepping away from the keyboard.

I thought that might be the case - but I was being tactful in blaming it on JVC :D

If you have a 75% white you can use that with the 75% colors - though it will be setting your reference L=100 at 75% white so not the perfect way to do it - but it would be just as valid as when the lamp is burned down a bit. Often it is useful to do both 75% and 100% tests because some manufacturers will pump up bright colors only.

If you can get hold of the swatch of different filters that Lee filters sometimes send out, you can try the filters that may work while having the software in continuous measure mode. Just watch the bars or whatever measures the RGBs and the filter that corrects them closer to optimal should be relatively quick to find. Once you have one (or a combination of two, lumens allowing), you can buy the actual filter knowing it's the right one..

Good idea !


Such as this one?
http://cgi.ebay./LEE-GELATIN-FILTER-K-IT-50-FILTERS-NR_W0QQitemZ110111351723QQihZ001QQcategoryZ79000QQssPageName ZWDVWQQrdZ1QQcmdZViewItem

Add com after http://cgi.ebay.

Gary Lightfoot and neilher brought up some quality concern of using Cokin filters and I'll report that their concerns were warranted. Late last night after the pj was on a several hours I noticed an obvious out of focus looking image, removing the filter returned proper focus. Keeping the filter in hand I moved it around the beam of light and the area of the filter previously passing the image not only unfocusses the picture but also distorts the image by bending the light. It would appear heat from the light has damaged the lens, I found a new portion of the filter to use temporarily but this filter should not be used long-term.

Does anyone know where to get expertice help regarding different filters?

That link doesn't work for me anbjornk (and I added the extra w too).

Hugh,

You may also find with new Cokin filters that there is more lens flare with bright objects in dark scenes than with a coated glass one.

Gary

That link doesn't work for me anbjornk (and I added the extra w too).

Guess the forum tricked me :) It's fixed know.

That looks like the one.

Gary

Thanks Gary.... Too bad it's sold :confused:

http://www.2filter.com/hoya/hoyawarmcool03.html has some nice selection of Hoya HMC filters (including 85A) reasonably. I bought my Hoya HMC FL-D from them 3 years ago. The filter is still going strong without any visible damage.

http://www.2filter.com/hoya/hoyawarmcool03.html has some nice selection of Hoya HMC filters (including 85A) reasonably. I bought my Hoya HMC FL-D from them 3 years ago. The filter is still going strong without any visible damage.


I bought my FL-Day from them for my HT1000, and have used it again on my H78 when I upgraded, and it still looks as it did when I bought it (must be 4 or 5 years now).

Gary

Hugh2

Did you get measures yet based on consistent pattern levels?

bought my FL-Day from them for my HT1000, and have used it again on my H78 when I upgraded, and it still looks as it did when I bought it (must be 4 or 5 years now).


Do you have before/after RGB charts?

I think I still have them somewhere, but they look the same as they both will show calibration to D65.

Gary

I think I still have them somewhere, but they look the same as they both will show calibration to D65.

Ok. The intersting part would be how the filter affects colorbalance.

I didn't record the before state, just the after, but I think I remember that the green was around 5% higher than red, and blue was around 20% higher than green on the RGB bars (Colorfacts) at 100% stim before I added the FL-D to an H78 (RGBs at max IIRC), and the immediate effect was that the green and red were pretty much balanced leaving mostly some blue adjustment (reduction).

Gary

I didn't record the before state, just the after, but I think I remember that the green was around 5% higher than red, and blue was around 20% higher than green on the RGB bars (Colorfacts) at 100% stim before I added the FL-D to an H78 (RGBs at max IIRC), and the immediate effect was that the green and red were pretty much balanced leaving mostly some blue adjustment (reduction).

Ok, thanks. So the filter didn't cut enough blue?

Hugh2

Did you get measures yet based on consistent pattern levels?

Yes I did, I've now somehow lost my intended post, not once but twice, after about half an hour of typing and getting f%^&*%&& charts posted. I'm about to have an f&*^** aneurism.

Hopefully I can muster the energy to get it down one more time. AAARRRR! :mad:

Ok for the third attempt, my wife is curious why I'm cursing so much, hang on a minute I have to fetch another beer.

OK I'm calm again but this will be short. I'm back after obtaining GetGrays calibration DVD which includes 100% color patterns for both primaries and secondaries which my DVE DVD does not. I have to add that this is a lovely DVD, very well laid out and all the nagging little wants in the back of my head seem to have been addressed.

Aided by Krasmuziks, what he refers to simple but, very revealing speadsheet which converts xyY data to LCH delta error data I've plotted the color response with filter and without. Essentially the measures plot changes or error in luminance, chroma, and Hugh :D , in a manner which is consistent with our perception of the same changes or error from standard from the rec709 standard.

Here it is:

Filtered first:

___dE(u'v')__dL____dC____dH

R__15.6____1.5___15.3___2.7
G__28.0____-1.3___28.0___0.0
B__4.2_____-1.7___2.3___-3.0
Y__20.4____0.0____20.4___0.7
C__15.6____-1.0___15.5___0.6
M__6.3_____0.5_____5.8__-2.4

No Filter

R__19.3____2.5____18.9____2.7
G__30.6____-1.3____30.5____2.5
B__4.3_____-3.3____-2.3____-1.6
Y__20.7____0.3____20.7____-0.2
C__16.5____-1.7___16.4_____0.6
M__8.9______1.0____8.1_____3.7


It would appear that utilizing this filter to tame green and blue optically instead of digitally does not trade off color performance for the 22% gain in contrast ratio. I hesistate to announce that the color signature has improved over JVC's intended outcome but relative to the rec709 standard things have improved somewhat with the filter. Both filtered and non-filtered means of calibrated can potentially deliver outstanding color decoder (brightess) and hue performance, the primary penalty of wide color gamut being errors in chroma of color only.

I've also plotted the color signature with color control at -30 and the results are very very interesting, with luck tomorrow I''ll have the means to put my theory to to the test that color saturation can be reduced without color brightness penalties with a little outside help.

Hugh=Hue - I love it - where is the LOL spittake emoticon on here ?

Oh minor typo - the du'v' is supposed to be dE(u'v') as opposed to dE(ab) to reference light vs. surface CIE formulas....

Anyway I see perceivable Red/Magenta Chroma diffs and a maybe a Green/Blue Chroma and Hue diff and certainly a Magenta Hue diff. No relative luminance diff to speak off. Since the diffs are right around the 3dE perceivability limits - are your eyes tracking what the numbers are saying?


So I guess you got lucky grabbing the orange filter first? Certainly the FL-D filter on the mostly correct SP7210 made things much worse - but I guess if you are off to begin with you are not doing much more harm to shift things around a bit more.

Hugh=Hue - I love it - where is the LOL spittake emoticon on here ? I'm still laughing!

Oh minor typo - the du'v' is supposed to be dE(u'v') as opposed to dE(ab) to reference light vs. surface CIE formulas.....

Fixed

Anyway I see perceivable Red/Magenta Chroma diffs and a maybe a Green/Blue Chroma and Hue diff and certainly a Magenta Hue diff. No relative luminance diff to speak off.

So I guess you got lucky grabbing the orange filter first? Certainly the FL-D filter on the mostly correct SP7210 made things much worse - but I guess if you are off to begin with you are not doing much more harm to shift things around a bit more.

That's correct, this filter was the first one I pulled off the shelf, I guess a little good luck was due. My outcome is pure fluke and the product of some sort of anti-anti-synergistic two wrongs making a neutral, probably never to be repeated again.

So using my subjective terms of the objective color grading based on CIE perceptual measures - the color decoding (hue and lightness) is imperceivable from perfect while the chroma (lightness/gamut) has nearly perfect blues, excellent magentas, greens barely adequate, yellows are good, and reds and cyans stepped up to very good with the filter.

Of course the above paragraph is not an official krasmuzik review since who knows if your calibration skills and gear be as good as mine :D


I would suggest trying a magenta filter deeper than a FL-D - that should help tug on the greens but will likely worsen the other colors - but maybe make for a more well rounded score.

So using my subjective terms of the objective color grading based on CIE perceptual measures - the color decoding (hue and lightness) is imperceivable from perfect while the chroma (lightness/gamut) has nearly perfect blues, excellent magentas, greens barely adequate, yellows are good, and blues and cyans stepped up to very good with the filter.

Of course the above paragraph is not an official krasmuzik review since who knows if your calibration skills and gear be as good as mine :D

Yah, I've have to admit it doesn't seem quite right does it but regardless if my skills are substantiated or not don't be dissin my gear man I've got at least a couple hundred invested. :D

But then again these measures along with your own grading system may very well respresent both accolades and critism of the same being.

Anyway I see perceivable Red/Magenta Chroma diffs and a maybe a Green/Blue Chroma and Hue diff and certainly a Magenta Hue diff. No relative luminance diff to speak off. Since the diffs are right around the 3dE perceivability limits - are your eyes tracking what the numbers are saying?
.

There was a time I believed my eyes were infallable but I've fooled myself many times and even with that in mind I must say that yellows look to be the exact balance of red and green. I've always felt that yellow looked a little too green on my previous system even when "calibrated" but now I can honestly say yellows now look "right". I'm also a little sensitive to cyan, which on my previous system felt was a little too blue, but again it looks to be a great balance of green/blue now which doesn't draw attention to itself anymore. I'm magenta ingorant and really don't care if it's off, I'm a water, sky, banana, lemon guy, who tf cares about magenta anyway :) but essentially yes my gut and eyes response is consistant with the measures.

What is a natural magenta anyways? It's the only color that is not in the rainbow! Infocus always got the secondaries perfect - so I am well tuned to those. Had a local meet and dialed in daGamePimps Mitsu - and one of the guys said - yuck what is up with those mustard yellows - even though they were perfect and we knew they were right - that guy thought they were wrong (but he will be sure to have me over to tune up his JVC now :D)

Anyways I have always called them as I see them - then had to go off and research CIELCH for a couple years to back up that indeed i called them as I saw them, then map that objective perceptual measures to a fair subjective grading - just to prove I was being fair when I said how it looked to me. But look who cares - the calibration thread has 30x more viewers and the owners thread has 100x more viewers....all arguing if the colors are perfect or not or if this or that guy is a paid shill or a competitors stooge. Sigh. :rolleyes:

But look who cares - the calibration thread has 30x more viewers and the owners thread has 100x more viewers....all arguing if the colors are perfect or not or if this or that guy is a paid shill or a competitors stooge. Sigh. :rolleyes:

I really don't get it either, kind of reminds me of when it seemed everyother post in the 4805 thread centered around flickering and the next firmware upgrade, I'm sure Bob Williams went to bat for us and pushed the next anti-flicker firmware upgrade through. The fix came to fruition but literally none of the complainers said a God damn thing, no thanks, that sucks, it's good, bad ,indifferent, nothing. I think Bob pretty much packed his bags from this site after that and I don't blame him one bit.

On second thought I'm not sure that has anything to do with anything but it felt great getting that off my chest.

I care.

Besides, I'm hoping you guys can figure out a way to save me from purchasing a Lumagen Radiance. ;)

In all seriousness, the RS1 calibration thread has pretty much been dead lately. Kras, except for you and Bob Sorel, Hugh2's findings on how the new firmwares color control affects both lightness and saturation has pretty much been overlooked entirely. I've been following this thread from it's inception and have wondered why there isn't more input here from some of the other RS1 owners with calibration knowledge. With two different firmware versions out there I guess there just aren't enough people on the same page yet and it's going to take some time to get this sorted out.

Hugh2,

Thanks for the effort you've put into this and for posting your results.

Btw, I'm still using the original firmware on my 4805 and have no flicker. :D

I have a Hoya HMC 81C coming my way. Let's hope I can use it :)

I have a Hoya HMC 81C coming my way. Let's hope I can use it :)

I have tried the Hoya 81C and base on my measurements, it does help improve contrast a little. My mid settings had the G & B reduction in the -50 to -60. With the 81C, I have both at about -20 plus. I have not measured the new contrast yet but base on the reduction of adjustments needed, it seems that I have improved on the contrast with about a 15% drop in lumens.

I had not measured the colours to see if there was a shift from this filter as well. but subjectively, it does seem to make the red more orange.

Oliver

I have tried the Hoya 81C and base on my measurements, it does help improve contrast a little. My mid settings had the G & B reduction in the -50 to -60. With the 81C, I have both at about -20 plus. I have not measured the new contrast yet but base on the reduction of adjustments needed, it seems that I have improved on the contrast with about a 15% drop in lumens.

I had not measured the colours to see if there was a shift from this filter as well. but subjectively, it does seem to make the red more orange.


Do you have before/after greyscale measurements?

I ordered a Hoya 77mm 85c yesterday but it's on back-order from the factory, I'll pick up something closer to the Cokin 85A I have as well.

The inside dimension of the RS1 lens shroud is about 78mm, press a very small amount of sticky tac into 77mm filter threads in a couple locations and it should press into place and stay put.

For reference from darkest to lightest in the 85 series:

85A...5500-3100 K
85b...5500-3200
85.... 5500-3400
85c...5500-3800

In torch mode my PJ measured approx 10500 temperature, the Cokin 85A filter alone reduced that to approx 5800

Smithfarmer, thanks. Don't thank me yet though as none of my measurements have been repeated for any sort of verification, for all we know I've got a bum sensor but I don't think that's the case.

It doesn't appear anyone is all that interested in whether the color control with new firmware does reduce the saturation or not. Most, I believe, have multiple sources which pretty much prevents any attempts of raising color brightness back up. I'm a little surprised no one with a second wave PJ has investigated my color control claims to at least verify or refute my findings whether they may find it a useful tool or not.

My projector measured just over 9000k in high colortemp, so I think a 81C will be a nice fit....

Ok, thanks. So the filter didn't cut enough blue?

Not on the H78, no.

I used an FL-D and an 81C (IIRC) together on an HT1000 and that gained a further 200:1 over the FL-D on its own, so if you can afford to lose the extra lumens, two filters may do the trick.

EDIT: Just remembered, it was a Skylight 1B and not an 81C that I used with the FL-Day. I did try the 81C but the FL-D was better with the DLP in this case.

Gary

Ok ! Thanks Gary.

I care.

Besides, I'm hoping you guys can figure out a way to save me from purchasing a Lumagen Radiance. ;)

In all seriousness, the RS1 calibration thread has pretty much been dead lately. Kras, except for you and Bob Sorel, Hugh2's findings on how the new firmwares color control affects both lightness and saturation has pretty much been overlooked entirely. I've been following this thread from it's inception and have wondered why there isn't more input here from some of the other RS1 owners with calibration knowledge. With two different firmware versions out there I guess there just aren't enough people on the same page yet and it's going to take some time to get this sorted out.


I am certainly interested in this, but I just don't have the calibration tools to know whether the color control is affecting saturation or not. It certainly has an impact on the colors, but I just don't know if it is affecting saturation or the lightness, or both.

We do need more users with calibration knowledge to get their hands on these 2nd wave units.

I believe Glenned should have his shortly, and I would expect him to be able to help sort this out and hope he will join in this discussion with Hugh and Kras.

I have a number of filters (81 and CC series) that I've used with cheaper projectors to improve CR. If my distributor doesn't screw up again with the next batch, I'll have an RS1 to try them with, but that's going to be at least another two weeks. I've been following Hugh's results and kras's comments with interest though.

Hugh2

Looks like there may be at least a few paying attention - might as well throw up numbers with the color control trimmed.....

This thread is very interesting. I'm not too concerned about improving my on/off any further, but if I can use a CCF to lower my black level while still getting somewhat close to the same lumens this trick will be worth it.

Still sounds like we are in the early experimental stages of determining what will work best and what the results are. I don't have any experience with CCF so I'll wait until you guys determine what seems to be the best filter/approach here. Then I'll give it a try and do all the measuring you're interested in.

I'll run some more numbers tonight with the color control reduced. I received the XA2 yesterday and quickly determined the Toshiba color control affects the primaries similar to JVC hence it can not be used to raise color brightness without the primaries returning to the oversaturated location. Green stopped a little short of it's previous mark but with all the primaires/brightness manipulation the end result was a clusterf&*$%* mess. Not the intended purpose of purchasing a PJ and player but I actually decided to watch a couple HD movies and though I was feeling a little bummed that my little experiment did not produce my desire result the HD images on the screen were (in my best Borat voice) "very nice" . Resolution, and CR accompanied with no scaling trumped any color errors, at least until the honeymoon wears off. :)

Though this thread is generally concerning using CC filters, since the filter is still in place I'll also post here the measures of dropping JVC's color control to -30.

For a quick preamble, a little while ago I noted that reducing the color control definitely appeared to move the primaries closer to the rec709 standard as shown in a CIE chart. I was hoping that this movement of primaries when combined with a source which could bring back up the color brightness could ultimately provide a method to reduce the measured and perceived color oversaturation on the JVC. As noted in the above post the Toshiba XA2 color control could not be used for this purpose.

Below are CIE u'v' charts, rather low rez images, showing the before and after results of reducing the color control to it lowest point. Looking at these alone would give the impression that the primary locations have overall improved. I've also included the xyY measures entered into Krasmuziks spreadsheet to help provide at least the potential for better understanding of what is occurring and show how difficult it may be to be color brightness back up.

Though this thread is generally concerning using CC filters, since the filter is still in place I'll also post here the measures of dropping JVC's color control to -30.

For a quick preamble, a little while ago I noted that reducing the color control definitely appeared to move the primaries closer to the rec709 standard as shown in a CIE chart. I was hoping that this movement of primaries when combined with a source which could bring back up the color brightness could ultimately provide a method to reduce the measured and perceived color oversaturation on the JVC. As noted in the above post the Toshiba XA2 color control could not be used for this purpose.

Below are CIE u'v' charts, rather low rez images, showing the before and after results of reducing the color control to it lowest point. Looking at these alone would give the impression that the primary locations have overall improved. I've also included the xyY measures entered into Krasmuziks spreadsheet to help provide at least the potential for better understanding of what is occurring.

I just finished with these same tests last night, had very similar results, and drew the same conclusions.

I just finished with these same tests last night, had very similar results, and drew the same conclusions.

It's great to have some confirmation, thanks.

It's great to have some confirmation, thanks.

Unfortunately I don't think we have any cheap solution to the oversaturation issue.

Unfortunately I don't think we have any cheap solution to the oversaturation issue.

I'm not sure there is any solution regardless of price. To this point I am not aware of any standalone CMS or CMS like functions included in a processor which operate as a true CMS.

Good demonstration though of the diff between a u'v' gamut diagram and Chroma. Chroma is composed of both saturation and lightness (13L*) which is how we perceive colors to be strong or weak AKA colorfulness. While it appears the colors got closer to the target gamut - the noticeable reduction in lightness has actually made the color way too weak.

If this control behavior was for individual colors - then it could be useful to create a compromise between slightly worse dL for better dC - you could see the big hit was to the dark colors RBM while the light colors CYG improved.

You can see why I have made such a large deal about this everytime someone says they found a control that moved the gamut in. Did they truly understand the cost of what they did - or get misled by only part of the picture?

Good demonstration though of the diff between a u'v' gamut diagram and Chroma. Chroma is composed of both saturation and lightness (13L*) which is how we perceive colors to be strong or weak AKA colorfulness. While it appears the colors got closer to the target gamut - the noticeable reduction in lightness has actually made the color way too weak.

If this control behavior was for individual colors - then it could be useful to create a compromise between slightly worse dL for better dC - you could see the big hit was to the dark colors RBM while the light colors CYG improved.

You can see why I have made such a large deal about this everytime someone says they found a control that moved the gamut in. Did they truly understand the cost of what they did - or get misled by only part of the picture?

I was thinking the same thing, separate controls for each color is needed whether in JVC's implementation or an outside brightness control each color needs adjustment separately at least in this example, sounds alot like a cms which obviously the XA2 does not have and could not overcome the brightness discrepancies. I think I'll plot JVC's color control in 2-5 step increments to see if it's possible find a setting which provides a reasonable balance across the board. I'll target approx equal errors between L and chroma first and see what that looks like.

This entire exercise has been very educational, I appreciate your input.

I think I'll plot JVC's color control in 2-5 step increments to see if it's possible find a setting which provides a reasonable balance across the board. I'll target approx equal errors between L and chroma first and see what that looks like.

This entire exercise has been very educational, I appreciate your input.

That would be great to know. Thanks to you (and kras for helping) for all your work on this. The only thing is, by the time I get my RS1, there'll be nothing left for me to try. :D

I have finally done a bit testing with the 81C filter...

Here's before and after adding the filter:

http://i176.photobucket.com/albums/w192/anbjornk/HD1RGBtracking_high.jpg



http://i176.photobucket.com/albums/w192/anbjornk/HD1colorbalance_highfilter.jpg

Below are CIE u'v' charts, rather low rez images, showing the before and after results of reducing the color control to it lowest point. Looking at these alone would give the impression that the primary locations have overall improved.

Does this mean that adjusting color to -20, versus at 0, actually makes the colors look more like they should?

I have finally done a bit testing with the 81C filter...

Here's before and after adding the filter:
Maybe it is my ignorance talking here, but in the 'before' sample...couldnt you just lower blue a little bit to get it tracking just fine?

Maybe it is my ignorance talking here, but in the 'before' sample...couldnt you just lower blue a little bit to get it tracking just fine?

The goal here is to optimize contrast :)

The goal here is to optimize contrast :)

Without compromising color!

RGB histograms don't cut it as they are only part of the story - you need to run your xyY measures for your RGBCMY gamut and plug them into the CIELCH spreadsheet linked in this thread and report back.

Am I the only one who thinks that this is a terrible idea?

At best using a filter will get you somewhat higher on/off CR. This projector already has extremely high on/off CR. I'm skeptical that any additional improvement in this regard would be meaningful. Furthermore, using a filter will usually substantially cut your available light output, will require recalibration of the gray scale, and may cause other optical problems, depending on the quality of the filter.

I just don't see it.

Am I the only one who thinks that this is a terrible idea?

At best using a filter will get you somewhat higher on/off CR. This projector already has extremely high on/off CR. I'm skeptical that any additional improvement in this regard would be meaningful. Furthermore, using a filter will usually substantially cut your available light output, will require recalibration of the gray scale, and may cause other optical problems, depending on the quality of the filter.

I just don't see it.

But what happens if you need to cut light output in the first place? Then this would be one of the best way as the HD1 does not have a manual iris control. Cutting light output with the additional advantage of increasing contrast. Double win isnt it?

Oliver

Am I the only one who thinks that this is a terrible idea?

At best using a filter will get you somewhat higher on/off CR. This projector already has extremely high on/off CR. I'm skeptical that any additional improvement in this regard would be meaningful. Furthermore, using a filter will usually substantially cut your available light output, will require recalibration of the gray scale, and may cause other optical problems, depending on the quality of the filter.

I just don't see it.

Tom - I'm with you that this is *probably* not worth the trouble and possible side effects. However there is a key benefit you may be overlooking and its not increased CR...

This approach (if it works with minimal side effects) could potentially provide a much improved absolute black level. So while I wouldn't care much about going from 15,000:1 to 20,000:1, it would be fantastic to see absolute black level drop significantly. That being said, someone reported that lumen loss was still in the neighborhood of 25% with this filter. Once I heard that I lost most interest in trying this. Still potentially a good outcome for others.

Without compromising color!

RGB histograms don't cut it as they are only part of the story - you need to run your xyY measures for your RGBCMY gamut and plug them into the CIELCH spreadsheet linked in this thread and report back.


I agree 100%. I will do some more measurements when I have time...

At best using a filter will get you somewhat higher on/off CR. This projector already has extremely high on/off CR. I'm skeptical that any additional improvement in this regard would be meaningful.

But in my opinion still not high enough.

Am I the only one who thinks that this is a terrible idea?

At best using a filter will get you somewhat higher on/off CR. This projector already has extremely high on/off CR. I'm skeptical that any additional improvement in this regard would be meaningful. Furthermore, using a filter will usually substantially cut your available light output, will require recalibration of the gray scale, and may cause other optical problems, depending on the quality of the filter.

I just don't see it.

This surprises me a little, not that you feel that this is not a good idea but because you, more than most, understand the concept of compromise to achieve the greater good. All else being equal, sure, sacrificing color makes little sense. Sacrificing color to obtain appropriate lumens on the screen to within standards which can help reduce the visibility of noise many see with this PJ to increase depth and 3D effect and things aren't quite so cut and dry, add in a couple thousand free points to the CR and things become even more less cut and dry should there be color or other compromise. Conversely would you calibrate a customers display to achieve that last few % for perfect color if that meant possible eye-burning lumens and a 25% cut in CR? Some would find that acceptable and some not so much. At this point I don't see where "recalibration of the gray scale" is an issue as it appears anyone experimenting has equipment.

Assuming my equipment and methods reasonably reflect reality I believe I have shown that at least with the filter I experimented with there was no sacrifice in color to obtain increased CR and a decrease in lumens to better levels in my setup. There was one negative which may be associated fully to the cheap filter I used caused increased obvious optical distortion with increased use. Again, assuming my measurements reflects reality, using this filter appears to little different than using a ND filter to cut brightness and seldom have I've read of any negative side-effects using a good quality filter for this purpose. I can only surmise that using a decent quality CC filter will reduce the negative result of using a filter. I've also learned that there indeed can be optical artifacts which at this point I can only attribute the specific (not glass) filter I used. Each end user has his/her own set of "meaningful" priorities for which they feel will offer to most life-like image factored on many variables, one being color accuracy.

Quite honestly I normally balk at putting anything additional in front of the lens except the screen and began this experiment primarily to provide myself with another project to keep myself occupied with the possible off-shoot that something could be learned (+ or -) from it. What I've learned so far is that, if you're a little lucky, using a CC filter tool to calibrate RGB balance and bring down lumens might yield surprisingly good results by maintaining CR close to torch mode levels and increase absolute black levels while doing so, and I neglected to mention that with this PJ, the reduction in absolute black level also decreases the visibility of bright corners should that be an issue with present setup. How much a PJ owner is willing to compromise to trans-morph to a seemingly better set of problems is anyone guess.

I look forward to trying the Hoya 85a filter I have coming in but it's on back-order till May 11. I also look forward to anbjornks color fidelity measurements.

Tom - I'm with you that this is *probably* not worth the trouble and possible side effects.


Worth the Trouble?? Most here spend tens if not hundreds of hours tapping on keyboards often about nothing at all, what's an hour setting up a filter.

The 25% lumen drop is with using an 85A filter which is very aggressive, the 85C is a much paler orange which should have far less lumen drop.

I look forward then to hearing about the results using the 85C. I'd be all for it assuming overall lumens falls less than 10-15% and ANSI CR and color is not significantly impacted. I've heard others say in particular that introduce any filter can really impact ANSI CR.

I look forward then to hearing about the results using the 85C. I'd be all for it assuming overall lumens falls less than 10-15% and ANSI CR and color is not significantly impacted. I've heard others say in particular that introduce any filter can really impact ANSI CR.

I've been reading the same thing about a reduction with ANSI CR which makes perfect sense and I've been meaning to measure it but feel I don't have the gear to do it properly (seems like spot meter would be ideal for this measurement). However I just put on a 16 square ANSI test pattern and measured with the meter facing the PJ lens about 1/4 distance from screen to projector with sensor centered in one of the squares. Typcial ansi tests require several measurements from different screen locations but this will have to suffice for now. I used the PJ's vertical flip option to switch the square from black or white.

ANSI CR no filter = 299
ANSI with filter= 276

An approx 8% reduction in ANSI CR with filter installed.

Just for conversion sake my first ANSI measurement with filter installed spit out a CR of 232 but I've doing a little work in the HT which I anticipated would create a little dust so put on the lens cap on the PJ but left the filter uncovered. After noting the lowish ANSI I checked the filter and there was a slight coating of dust on it which I cleaned off most with some air after which I attained the 271 measurement. Keep your room and optics as dust free as possible, even a small amount of dust is an ANSI killer!

I've been reading the same thing about a reduction with ANSI CR which makes perfect sense and I've been meaning to measure it but feel I don't have the gear to do it properly (seems like spot meter would be ideal for this measurement). However I just put on a 16 square ANSI test pattern and measured with the meter facing the PJ lens about 1/4 distance from screen to projector with sensor centered in one of the squares. Typcial ansi tests require several measurements from different screen locations but this will have to suffice for now. I used the PJ's vertical flip option to switch the square from black or white.

ANSI CR no filter = 294
ANSI with filter= 271

An approx 8% reduction in ANSI CR with filter installed.

Just for conversion sake my first ANSI measurement with filter installed spit out a CR of 232 but I've doing a little work in the HT which I anticipated would create a little dust so put on the lens cap on the PJ but left the filter uncovered. After noting the lowish ANSI I checked the filter and there was a slight coating of dust on it which I cleaned off most with some air after which I attained the 271 measurement. Keep your room and optics as dust free as possible, even a small amount of dust is an ANSI killer!

Very encouraging. Ideally the ANSI CR measurements would be taken very close to the lens 6-18" with treatment on the ceiling above the meter assuming the pj is ceiling mounted and within a foot or so of the ceiling. But even with your rough measurement it sounds pretty good. This is with the more aggressive filter right? What about the more pale filter you mentioned - is that on tap for testing?

Very encouraging. Ideally the ANSI CR measurements would be taken very close to the lens 6-18" with treatment on the ceiling above the meter assuming the pj is ceiling mounted and within a foot or so of the ceiling. But even with your rough measurement it sounds pretty good. This is with the more aggressive filter right? What about the more pale filter you mentioned - is that on tap for testing?

I ran the test again after giving both the lens and filter a blast of air which increased the numbers slightly which I've edited my previous post with. I'm a little surprised, I thought the ANSI with filter would be less than that. Yes these measurements are with the Cokin 85A filter which I believe is the most aggressive orange filter of this series, I have a large Hoya 85C on order which I anticipate will have less than half the lumens cut than the 85A but with a slightly different green blue filtering ratio which may or may not work as well for my situation which could alone impact CR measurements. I should have the Hoya middle of May and will post some measurements when I do.

This surprises me a little, not that you feel that this is not a good idea but because you, more than most, understand the concept of compromise to achieve the greater good.It's not the concept I have a hard time with. It's the implementation. For this particular PJ, I just doubt that a small increase in CR would be visible, whereas the drop in light output and potential optical distortions would be. I just don't see how a greater good is achieved. It sounds more to me like an obsession with tweaking for tweaking's sake.

It sounds more to me like an obsession with tweaking for tweaking's sake.

What's wrong with that? :D

It's not the concept I have a hard time with. It's the implementation. For this particular PJ, I just doubt that a small increase in CR would be visible, whereas the drop in light output and potential optical distortions would be. I just don't see how a greater good is achieved. It sounds more to me like an obsession with tweaking for tweaking's sake.


You are correct the reduction in light output with this particular filter in place is quite noticeable but there are many instances where this can be beneficial. You are implying that maximizing or maintaining lumen output is the only option for all installations, any methods employed to reduce lumen output therefore is undesirable. Using filters to cut lumen output is fairly standard and accepted practice, the benefits can outweight the negatives.

I'll state again that I've found a few positives using the filter:

1- Increase CR of 20 %. whether it's visible is debatable but I'd could never imagine an instance where an owner or calibrator would throw away CR by 20% if it could be avoided and just say you can't see it anyway.

2- Drop in lumens, same effect as employing an ND filter. Some situations could welcome this.

3-Decrease visibility of bright corners.

This thread was started to provide a few measurements in an attempt to quantify the results of using the filters as opposed to relying on intuition of their effects. In the process I have noted some subjective positives and a couple negatives in my setup which may or may not be Cokin filter specific. If you wish to dismiss what I, at this point, subjectively feel may be an improvement that's fine, hopefully whatever measurements are taken by myself and others which may be helpful to those interested. I note from your site that you are ISF certified, have you first-hand witnessed and/or measured the negative effects of using filters?

Tweaking for tweaking's sake....never! :D

I ran the test again after giving both the lens and filter a blast of air which increased the numbers slightly which I've edited my previous post with. I'm a little surprised, I thought the ANSI with filter would be less than that. Yes these measurements are with the Cokin 85A filter which I believe is the most aggressive orange filter of this series, I have a large Hoya 85C on order which I anticipate will have less than half the lumens cut than the 85A but with a slightly different green blue filtering ratio which may or may not work as well for my situation which could alone impact CR measurements. I should have the Hoya middle of May and will post some measurements when I do.

Thanks - these measurements seem right on target. For instance Greg measured about 300 ANSI CR and I did as well. Having you measure about the same then gives us confidence in the measurement with the filter. 8% loss is not a show stopper for me so that is encouraging indeed.

A few questions:

1) Sounds like the filters take a while to get / ship - middle of May? :confused: How much do these run?

2) I'd love to see a CIE chart without the filter vs. with if you have an opportunity to snap one off at some point.

3) Is there ANY impact on the razor-sharp focus or clarity of the image when the filter is used? Even the slightest noticeable amount would be a show stopper for my tastes.

4) How do you have the filter attached to the RS1? My understanding is that because of the notch on the RS1 a filter does easily slip/fit over the lens?

5) I recall reading that these filters can change the color output over a relatively short amount of time due to usage/heat or whatever - causing the color to drift. Any truth to this?

Thanks for keeping us posted. I'll be real curious about how things work out with the 85C compared to the current one you are using.

It's not the concept I have a hard time with. It's the implementation. For this particular PJ, I just doubt that a small increase in CR would be visible, whereas the drop in light output and potential optical distortions would be. I just don't see how a greater good is achieved. It sounds more to me like an obsession with tweaking for tweaking's sake.

Tom as I mentioned earlier I agree that there is likely little or no perceivable benefit from the increased on/off CR. However there is likely a huge benefit on fade to black scenes due to a significant lowering of absolute black level, without (hopefully) too much lowering of the white level (to me I'd accept up to about 10-15% loss as a tradeoff).

3) Is there ANY impact on the razor-sharp focus or clarity of the image when the filter is used? Even the slightest noticeable amount would be a show stopper for my tastes.

5) I recall reading that these filters can change the color output over a relatively short amount of time due to usage/heat or whatever - causing the color to drift. Any truth to this?

Since I don't have an RS-1 yet, I can't speak to the other questions, but from using a number of filters with other projectors, I've never had any reduction in sharpness using a good quality filter. A glass filter like the ones talked about here will not change over time. Some of the resin and gel-filled fillers are susceptible to change however, which is why their use with projectors is not recommended.

As an aside, I've never used an 85 series filter, as I've had good results with the 81 series, but it looks like the RS1 may match up better with an 85. I'll eventually check a few out and see what does the best job.

Thanks for all the info guys. :)

.......A few questions:

1) Sounds like the filters take a while to get / ship - middle of May? :confused: How much do these run?

2) I'd love to see a CIE chart without the filter vs. with if you have an opportunity to snap one off at some point.

3) Is there ANY impact on the razor-sharp focus or clarity of the image when the filter is used? Even the slightest noticeable amount would be a show stopper for my tastes.

4) How do you have the filter attached to the RS1? My understanding is that because of the notch on the RS1 a filter does easily slip/fit over the lens?

5) I recall reading that these filters can change the color output over a relatively short amount of time due to usage/heat or whatever - causing the color to drift. Any truth to this?

Thanks for keeping us posted. I'll be real curious about how things work out with the 85C compared to the current one you are using.

1) I'm in Canada and the Canadian online dealers supplier was out of the large 77mm filters. I suspect USA purchases would be quickly supplied. As usual I paid too much, good filter price of about $51 CAD plus crazy shipping and crazier tax. A fact of life living in Canada.

2) I posted a couple CIE charts on the first page of this thread of what you're looking for. Are those what you're looking for?

3) Anything which reduces clarity or sense of focus drives me nuts so I was expecting this to be a problem. Looking at the on screen menus I see no changes whatsoever, the text is still razor sharp. Watching movies I at times feel there may be loss of optical resolution, other times I'm convinced there is not. Without matching brightness levels and eliminating personal bias it may be difficult to ascertain for sure but I'm leaning towards the "no loss" camp. (this is when the filter is not suffering the effects of heat)

4) In post #14 I have a photo of the temporary filter and holder, this hangs in front of the lens via a piece of tape. The filter holders circumferance is the same size as the PJ lens. The new Hoya filteron order is 77MM and I measured the PJ shroud at about 78MM, my plan is to use a very small dab of tac "n" stick on the filter threads and push in in place.

5) I haven't noticed any drift from the Cokin filter but there does seem to be a amount of color variation across the screen and in the corners. This could be fault of the filter but more likely non-uniformity of the panels.

lovingdvd

He is not posting CIE xy charts anymore because of coming to the understanding how they have nothing to do with visual perception. Those that calibrate only to the CIE chart are making the picture visually worse - it does not consider color brightness for decoder levels - or the perceptual differences in saturation influenced by brightness. He is posting LCH data instead - which covers all three perceptual dimensions - lightness, chroma and hue.

So far a reduced color control combined with the filter - slightly improving light colors (CGY) and worsening dark colors (BMR) for overall little chroma difference at a cost of color lightness reduced off the standard. The filter itself causes color errors to shift around - but arguable if that is percievable or not. Hugh2 owes a run with different levels of color control to see if a compromise setting can be found.

lovingdvd

Hugh2 owes a run with different levels of color control to see if a compromise setting can be found.

I apologize to MikeSRC, I sorta forgot about posting that, I ran the test last week but there's nothing of value to report, no compromise could be found. The color control does not function in a linear manner or equally for saturation and brightness. The primary color locations move relatively little for the first -14 or so clicks then really begin moving between that and -30. On the other hand color brightness is so sucked out by -15 where the primary movement gets ramped up that any sort of middle ground is impossible.

If there were more primary movement between -4 and -8 then perhaps a good compromise could have been reached but such was not the case.

....So far a reduced color control combined with the filter - slightly improving light colors (CGY) and worsening dark colors (BMR) for overall little chroma difference at a cost of color lightness reduced off the standard. The filter itself causes color errors to shift around - but arguable if that is percievable or not....

Just wish to clarify that when I introduced the filter and took measurements the color control was not manipulated in any way from the pre-filter measures. The only adjustments were to the RGB controls to get gray back to D65 or thereabouts. Any changes in color lightness is do to either the filter, RBG controls, equipment tolerances or UBD error, but definitely not the color control.

Here are my most recent numbers again, posted in the previous page.

Filtered first:

___dE(u'v')__dL____dC____dH

R__15.6____1.5___15.3___2.7
G__28.0____-1.3___28.0___0.0
B__4.2_____-1.7___2.3___-3.0
Y__20.4____0.0____20.4___0.7
C__15.6____-1.0___15.5___0.6
M__6.3_____0.5_____5.8__-2.4

No Filter

R__19.3____2.5____18.9____2.7
G__30.6____-1.3____30.5____2.5
B__4.3_____-3.3____-2.3____-1.6
Y__20.7____0.3____20.7____-0.2
C__16.5____-1.7___16.4_____0.6
M__8.9______1.0____8.1_____3.7

Hugh2

I am lazy - can you do a delta dE/dC/dL/dH to show the difference the filter created (subtract the pre/post data)

No problem. Positive numbers denote impromement with filter, negative numbers a worsening with filter.

___ddE(u'v')_ddL__ddC___ddH

R__3.7______1.0__3.6_____0
G__2.6______0____2.5____2.5
B__0.1______1.6___0____-1.4
Y__0.3______0.3___0.3___-0.5
C__0.9______0.7___0.9____0
M__2.6______0.5___2.3___1.3

I've been reluctant to make any claims or proclamations with respect to my measurement result without corroborating measures so in an effort to appease my own doubts of accuracy and relevance or, at the very least, consistency of my measures I ran a complete new set of and ran them through Krasmuziks spreadsheet. Keep in mind that it's been two full weeks since I ran the measures posted just above, my tripod/sensor is in a slightly different location.

I ran 100% windows and calibrated the 100% white window pre-filter to dE .26 to D65, and managed to get 100% white with filter to dE .14 to D65. I have not touched the color control and didn't even check to see if all was still ok.


Filtered first

__dE (u'v')_dL____dC_____dH
R___17.6___2.1___17.3___2.7
G___28.5___-1.1___28.4___0.4
B___5.8___-1.0____4.6____-3.4
Y___20.8___0.2____20.2___-4.8
C___16.4 ___0.8___16.0___3.1
M___7.7____1.4___7.5____-0.9

No filter

R__20.7___2.9___20.4____2.7
G__31.1___-1.2___30.9___2.9
B___3.7___-3.0___ -0.7___-2.1
Y___20.5___0.4___ 20.5___-1.4
C___17.3___-1.6___17.1___1.8
M___10.6 ___.6___ 8.6_____6.0

And the "delta dE/dC/dL/dH to show the difference the filter created"

___ddE(u'v')_ddL__ddC___ddH

R__3.1______.8___3.1_____0
G__2.6______0.1__2.5____2.5
B__-2.1_____2.0__-3.9____-1.3
Y__-.3______0.2___0.3___-3.4
C__.9______0.8___1.1____1.3
M__2.9____-0.8___1.1____5.1

With the exception the barely perceptible changes (about 3 dE) of yellow/magenta the relative dE changes from the filter are very consistent compared to my previous results Essentially, the end result of using the Cokin 85A filter with my RS1 has measureably improved on average color chroma, lightness and hue. Any measured change ultimately is under delta of 3 which for most intent and purposes is imperceptable to the "Hughman" :D experience even in side by side comparison.

I think I found my new moniker. :)

At some point during this thread I stated I'd attempt to find a compromise using the color control which yields the least average delta error between color brightness, color saturation and color hue. I did some quick testing last week focussing primarily on the chroma movement of gree and reported no comprmise could be found but this was kind of a knee jerk reaction to just viewing the numbers in Krasmuziks spreadsheet accompanied with viewing the shifts within the CIE charts but I did not actually average all the results.

I felt I short changed a few including myself so I again ran the numbers tonight but calculated the averge delta error to determine what I originally indicated I would. I measured the xyY values while reducing the color control from -2, -4, -6, -8, -10, -15, and calculated the average error of lightness, chroma and hue for each position to determine which offered the best compromise. I re-established 100% white level before each run as lumens increased slightly throughout the test. To calculate average I performed root mean square (RMS) calcs from the dEu'v' which has accounted for the weighting assigned to LCH as they combined relate to perception.

Here are the RMS results, the first at -2 which is the proper color calibation using DVE filter and Getgray disk. on my setup which does give the best overall lightness error.

-2, RMS dE= 17.9
-4, RMS dE= 16.4
-6, RMS dE= 15.4
-8, RMS dE= 14.8
-10 RMS dE= 15.4
-15 RMS dE=16.0

I'll also submit a straight average of dEu'v' for each color position:

-2 average dE=16.1
-4 average dE=14.2
-6 average dE=12.4
-8 average dE=12.9
-10 average dE=11.2
-15 average dE=15.3

Utilizing the LCH model which takes into account color brightness and it's perceptual effect on saturation it's stands to reason that the goal would be to minimize the average delta error for primary and secondary colors lightness, chroma and hue. With that goal in mind setting the color control between -8 and -10 appears to the sweet spot in my setup and accounts for the lowest RMS and average delta error taking all the above factors into account.

I'm quite surprised at these results, assuming the measurements and calculations are accurate then using the LCH model to calibrate overall color accuracy shows the best perceived result could be anywhere between -4 and -15 on the color control. The presumably filter calibrated result of color control at -2 would appear to very setting not to use if the intent is to maximize overall color accuracy.

Hughman (Hugh2)

Usually RMS (root mean square) is used rather than average when you have negative values...statistically better. You only need to take RMS of dE since dE is the vector magnitude of dL, dC, dH already. I was going to update the spreadsheet - but Excel has no built in RMS - so it would be work to do later!

Have you tried it with the filter that bettered it for light colors at the expense of dark colors? The color control seems to compensate for the dark colors so it might be a matched tweak!

Hughman (Hugh2)

Usually RMS (root mean square) is used rather than average when you have negative values...statistically better. You only need to take RMS of dE since dE is the vector magnitude of dL, dC, dH already. I was going to update the spreadsheet - but Excel has no built in RMS - so it would be work to do later!

Have you tried it with the filter that bettered it for light colors at the expense of dark colors? The color control seems to compensate for the dark colors so it might be a matched tweak!

Stats 101 is now starting to come back, it's been a welcomed very long time. I've updated my post to reflect a RMS calculation on dEu'v'.

I was hoping these results clarify things for me but it appears the opposite has occurred. It appears there can be a wide range of color control setting which achieve compromised but reasonably equal calibrated results. Think I'll need a few days to digest this.

My measured results were with the filter installed.

I'll post the raw dE data for viewing for the filter calibrated -2 color setting which uses lightness as the determinant and the LCH model showing the best overall color compromise at a -10 color setting:

color control -2

........dEu'v'.....dL.....dC........dH
R......17.4.....2.3......17.0......3.2
G......28.2......-1.2......28.2......0.4
B......5.7......-1.0......4.5......-3.4
Y......20.9......0.4......20.5......-3.9
C......17.3......-0.6......16.9......3.7
M......7.1......1.6......6.8......-0.9

color control -10

........dEu'v'.....dL.....dC........dH
R......4.1......-1.7...... 2.1......3.1
G......25.0......-2.3......24.9......0.9
B......11.1......-4.7......-9.8......-2.6
Y......19.7......0.6...... 19.3......-4.2
C......15.9 ......-1.3......15.5...... 3.1
M......2.3......-2.1...... -0.9......0.6

I beg anyone with this PJ (JVC RS1) and measurement equipment to please perform similar measures and post your results. Not that this is life and death or anything but if other projectors behave in a similar manner then perhaps a range of color control settings could be found which could be effectively applied by any user asking how to best set the color control on the RS1 for maximum color fidelity. At this point I'm inclined to suggest a -10 color setting would be suitable at least for my system.

... At this point I'm inclined to suggest a -10 color setting would be suitable at least for my system.

this is over my head.
do you mean to simply go to the image menu and set color to -10?
what do you mean by "suitable at least for my system?" is a filter required?

Hi,

Yes, the color control I'm referring to is the one in the user "image" menu.

It has not been established yet but the 2nd wave pj's color control,which have the newer firmware, may operate differently than the first batch, therefore my control function may not be representative of all the RS1's out there. Without corroboration, my results are specific to my system only.

I did perform the measures with the filter installed and wil do a run without the filter soon but don't expect huge differences but ya never know.

I'm not as picky as many here, interested in some help for the obvious situations where oversaturation occurs. Not understanding all the posts here, is there some filter(s) that help make it better?

Unfortunately I don't think we have any cheap solution to the oversaturation issue.

I completed the color control measurements without the filter attached to the PJ. Though as I've stated above these measurements are relevant to my system only, however, with the many anecdotal reports of reduced color settings improving the perceived color balance I suspect other PJ's are reacting similarly. Both RMS and averge provide the same relative result so I'll only post the average but I've thrown in an additional measurement at -12.

-2, average dE=16.9
-4, average dE=16.3
-6, average dE=15.2
-8, average dE=14.7
-10, average dE=12.4
-12, average dE=14.6
-15, average dE=15.7


So regardless if the filter is installed or not the best color setting which minimizes perceived color error is at or around -10.


Stew M, the filters purpose has nothing to do with manipulating saturation levels. The filters purpose is to bring down excess blue and green more in line with red and do this optically instead of digitally with the PJ's RGB controls. This method of equalzing RGB levels increases contrast ratio. Sorry for the confusion, this thread is dealing with both topics.

Hughman - great work on all this and thanks for the regular updates. The one question that keeps running through my mind as I read these posts is whether the error in Y, introduced by changing the color control, has a detrimental affect on PQ.

I haven't measured it recently but as I recall even changing the color control a few clicks lower caused Y to quickly become way off from the spec. So OTTOMH I'm thinking that at -10 the Y values are perhaps 20% too low - maybe more?

IIRC the compromise/tradeoff being made for this is based on finding a balance between 3 different properties (such as Y vs. CIE points vs. something else). My interpretation is that in this model all 3 factors are being equally weighted in importance. However, I do not know if that is indeed the case.

For example if Y has a more significant role than another factor, then I'm not sure a model that averages all 3 equally to find a compromise dE is ideal. Then again if it turns out Y is the least important factor, then that would be a big plus in favor of this tweak.

dE is equal weighting of the perceptual components dL, dC, dH - in terms of it being a vector magnitude. So a 5% in lightness is just as annoying as a 5% hue or 5% chroma shift if that was the only error - the dE=5. However a 5% shift in all three is worse than a shift in each - the magnitude is now dE=8.6. (I sometimes use % rather than writing out delta units - it just reads better - though technically % is not a correct unit)

Keep in mind that we are using L* not Y. Y is the physical measure of brightness - that goes up quickly as a power curve - L* is the perceptual measure including the perceptual gamma - it goes up quickly in blacks then slows down in greys and whites. Basically it is like a mirror of the power curve - more like a square root curve. A huge change in absolute Y on the bright side is barely perceivable when you look at it as a perceptually relative L*. In fact a 20% Y cut is actually <9% cut in L*!


I think you will see those who adjusted per the CIE 1931 gamut chart and ignored Y are way out there at -20 and -30. But those who adjusted by eye - got the -10 that Hugh found thru perceptual measurement/analysis was the best compromise of gamut and decoding.

Thanks Krasmuzik, I was hoping if I procrastinated long enough you'd offer up an understandable explanation.

Lovingdvd, the answers to your query have been posted in this thread and I'm hardly one to explain the mathematics so I'll refrain. If you require more info you'd be well served to do an LCH search under Krasmuziks name as he has a number of posts outlining the LCH model and it's advantages. Further up in this page you'll see a chart with dEu'v', dL, dC and dH numbers which should answer your brightness question.

You have the equipment, why not run a few measurements? I would welcome any measurements whether they corroborate my findings or not.

Krasmuzik, I'm getting the impression that using the LCH model to locate the best perceptible compromise between color saturation and brightness errors is a relatively new practice for display calibration. Was your inclusion of this tool influenced directly by your formal training or something you picked up on later on ?

What I need now is to have your spreadsheet or essence of integrated into my calibration software, I'm quickly running out of paper and pens.

Measurement of LCH to video calibration came from my own desire to create an objective perceptual coding system - since I and any other calibrator gets tremendous flack when we use subjective words to describe what we see - as usually those words will not agree with a PJ "champions" words when they have self or biz justification blinders on. This became evident after I conducted a series of shootouts with local AVSers - and made the mistake of asking them to post their impressions - some of whom have never posted again as a result.

LCH is not covered as well as CIELUV though - so it took a number of references for me to piece together the math. Bruce Lindblooms and Poynton reference actually has LCh - where h is degrees or radian angle - it is not linked to the dE formula as it just the polar coordinate form of L*u*v* (what is the magnitude of an angle?!).

I found what I needed in an obscure Color Science Matlab reference - that gave the math for H so that LCH and LUV result in the same dE. Sometime after that I saw gregr started using u'v' gamut charts at WSR - and I sent him an early version of the math for review. He noted that he is not convinced u'v' is any more perceptually correct than xy so he flip-flops which chart he uses. He was right - the more perceptual version is actually u*v* - which is only a target - not a gamut - especially in video with RGB components that are standard specified for unequal brightness.

I have a Digital Pictures text from my computer engineering masters degree that covers a lot of psychovisual science as background for the compression algorithms. It covers the various forms of CIE charts - xy, u'v' and u*v* and how the Munsell representation of color maps to them - and shows how u*v* is the most perceptually uniform. Though it is still not perfect since Munsell is a color circle notation and there is no measurement system that results in perfect circles - for surface colors CIELAB has been tweaked since 1976 (with tweaks that diverge based on industry) but CIELUV (used for colored light/video) has not been tweaked. But I had no intention of inventing anything new - this spreadsheet is stock CIE 1976 formulas.

So I started testing it on my calibration customers since gregr himself seemed ambivalent about it and thru my own education knew it still ain't perfect!. I came up with my own chart formats thru that process with the goal being I don't want to explain color science and video engineering so they can understand what calibration did for them. It is thru that process that I began to appreciate how closely it maps to human perception. Once I finalized the presentation thru feedback on calibration jobs I started posting calibration reviews on my website using CIELUV and CIELCH.

ISF does not teach any of this color science - nor do advanced calibration seminars. Even today you don't see xyY measures for color in reviews - let alone the more perceptual LCH version - I would be happy if we get them to stop meaningless 6500K charts (the only failing ISF question - why is 6500K not a calibration measure when D65 is?) Red push never even seems to be measured - it seems to be adjusted thru AVIA filters or reference viewing! The most annoying is reviewers that show the same CIE gamut charts for the same PJs - then have completely different subjective interpretations of how off they are! That is where my subjective grading method came from - but I tried to make it as tolerant as possible (my personal version would be much more harsh!) - using dE RMS for final grades and assigning ranges for subjective qualifiers - but you still need the LCH breakdown to explain the errors.

I posted the spreadsheet to educate regarding the math - I just don't want to see people start selling it by plugging in colorimeter readers. If they want to use the spreadsheet to create such a product - they cannot. What they can do is go back to the references and learn it themselves and do their own implementations, but even then my chart format is my copyright - they need to come up with their own designs. I reserve the right to make money from my work and not allow anyone else to - they have to do their own work if they want to make money.

ColorFacts has LCH in its raw data window - but never really worked for me. It also has u'v' gamut diagrams - it is missing the L*u*v* and LCH color targets for decoders and gamuts that indeed would be useful in calibration - though it really has to be a wizard since these sort of adjustments requires retaking the RGBCMYW readings each time - as you have learned! I basically just use ColorFacts for its link to sensors/generators and dump out raw data for my own software. If someone has a reference CMS and wants their color calibrated - I charge extra for using my methods instead of the usual AVIA filters and reference viewing - they are getting more than an ISF certified calibration after all!

BTW I don't use this spreadsheet in my own calibrations. I reserve the right for there to be bugs in it as a result - I already found one and posted an update. There could be more - I only slapped it together as a result of the recent interest in color measures because of the JVC hype - it is not something I use myself - it is only an educational reference. Like all good textbooks - it may be revised.

Wow, very interesting. Thanks for the reply. When I mentioned the spreadsheet being used in a program I had in mind that you would be paid for it's use if used commercially.


The spreadsheet is most definitely educational and imo a very useful tool. While ideally there would never be a need to make compromises, PJ's such as the JVC make it clear that indeed some compromise may be necessary and luckily with this pj can be made to to maximize the perceivable result. The LCH model has potential to be a valuable tool when used for this purpose and I'm surprised and a little dismayed that some would dismiss the method. Calibrating the chain is the game, if compromise is required I see nothing incorrect with using a psychovisual approach to finding the best compromise as it is a human brain at the end of the chain. To ignore or dismiss outright a seemingly objective tool which can ultimately be used for this purpose seems a little contrary to the ultimate goal of a calibrator. IMO, your method is a far more reasonable and enlightened approach than simply chanting the mantra and claiming it can't be done.