AVS Forum banner
1 - 20 of 749 Posts

·
Registered
Joined
·
1,347 Posts
Discussion Starter · #1 ·

Note: Even though I mention some Epson projectors specifically, this method can be applied just as effectively to all projectors. In fact, this calibration philosophy is applicable to all display devices.


Stereomandan’s Calibration Method for Epson 1080 (partial), 1080UB, 6100, 6500UB, 7500UB, 8500UB, 8700UB...



From my discussions with folks here, I’ve discovered that the CMS (Color Management System) behaves the almost the same on all the projectors listed above (except the 1080 which doesn't have brightness control in the CMS, so a Epson 1080 owner will only get partial benefit) This means that my method listed below will perform roughly the same with any of these projectors. (Personally, I own the 1080UB the early brother to the 6500UB, 7500UB, 8700UB...)


As a side note. I have not had a chance to fool around with the THX mode on the newer models. I believe this mode is closer to the correct REC.709 standard than other presets on older models, but still can benefit from this method.

Background:

While performing detailed calibration of my 1080UB, I discovered that I could achieve what most would seem almost a perfect result. My primary and secondary color and brightness lined up perfectly with the REC.709 reference points, my gamma tracked dead-on 2.22, and my grayscale was fantastic at 6500K with a dE of less than 2 from 20% to 100% stimulus. Here is an example of my calibration, which I was extremely happy to achieve. Doesn’t get much better than that huh? Well, read on.



The problem:

I noticed that areas of scenes looked washed out(gray), and as if color had been reduced. The picture was better than the "out of the box" settings though. While the picture looked good, it lost a lot of that colorful POP wow factor. It was most noticeable in mildly lit scenes. When colors were subtle, they looked washed out. The problem was particularly noticeable with skin tones, which are critical. Faces looked too gray, and the picture just looked flat. Outdoor, well lit scenes didn’t seem to suffer as much.

What did I do?:

I tried to understand why colors looked washed out. This led me to the Color Saturation Windows in the downloadable AVSHD REC.709 disk found here:

http://www.avsforum.com/avs-vb/showthread.php?t=948496


I had been using this disk for my calibration, but had simply been using the 75% or 100% Brightness Color windows for calibration. This is what is commonly used, and the standard method for calibrating. See the top two arrows in the picture below:




For more background information, look here at Kurt’s Dummies Guide for calibration, a fantastic source of information.

http://www.curtpalme.com/forum/viewtopic.php?t=10457

Important Information before you read on:
Color terminology. I will be discussing Color Brightness Windows, and Color Saturation Windows. They are NOT the same. When most people talk about using 75% or 100% color windows for calibration, they are talking about the Color Brightness windows. The saturation does not change between these 75% or 100% color windows. (the x, y locations remain the same.)


Using my calibration method, you will use the 75% Saturation windows (which are at 100% Color Brightness). I’ll explain why later, and where you can find the patterns.


In order to understand what I mean, let’s take a look at the color gamut triangle. Shown below is the color gamut from above, but with some explanations. Take the green primary for example (at the standard REC.709 reference point.) Let’s say you were to pull up a 100% brightness color window for green. If you measure the Green location to be outside the REC.709 triangle, then it is oversaturated. If you were to measure the green primary and it was inside the REC.709 triangle, then it is undersaturated. Adjusting Hue spins the measured point around the D6500 reference white point, as shown. The goal is to get the measured value of green to match the reference point of the test pattern. This chart does not show the brightness of green, another critical measure. You can have green perfectly saturated and the correct hue, but it can still be to too light, or too dark. This is why there is a x, y location for all colors, but also a Y (Brightness) value. All three have to be set correctly to have an accurate color.




O.k., with that said; let’s say you want to find out how accurately your projector displays more subtle colors of green, closer to the center 6500K white point in the color gamut. Are there test patterns for this? Yes, but the only ones I’m aware of are on the AVSHD REC.709 disk. They are listed in the Color menu, under saturation windows, as shown below.(the bottom arrow) Here are where the 75% Saturation windows are located (as well as 0%, 25%, 50%, 75 and 100% color saturation windows for all primaries and secondaries.) All of these patterns use 100% brightness (Y) as their reference. The patterns also assume your display gamma is 2.22. (By the way, the 6500K white point, shown in the photo above, is where all of the grayscale measurements are located, from black all the way on up the grayscale to white. This gray, "middle area", of the triangle is where there should be no noticeable color.)




This is where all of these saturation windows are located on a color gamut chart:




Don’t confuse these with the standard 75% and 100% Color Window patterns shown below. These are the color windows found on most calibration disks. These color windows are only at the outer edge of the color gamut triangle, but the brightness (Y) is either 100%, or 75%. Here are where they are located on the AVSHD REC.709 disk.




So, what happens when you calibrate our Epson projectors to the standard color windows? Take a look below. The 100% saturation points, at the outer edge of the triangle look great, but look at the 75%, 50%, and 25% saturation points for all the colors. Pretty surprising huh? Let’s take green again for example. When green is supposed to be 75% saturated, it will really only be close to 50% saturated! The same holds true for other colors. This is why I noticed the colors looking gray and washed out! It was really happening, as the measurements show.




So what do we do? Well, after studying my calibration files, I noticed that the 0, 25, 50 and 75% saturations seemed to perform o.k. after some adjusting, but then all heck broke loose at 100% saturation and became oversaturated. So I thought, well, maybe I can at least get the 75% saturation gamut(and lesser saturations) to look great. This 75% gamut is outlined by the light gray triangle in the picture above. This makes up a LOT of the available colors to choose from. The 100% saturation points will be off, but maybe this is overall a better solution.

So here are the results:

The 0, 25, 50, and 75% saturation points line up fantastic, and the 100% points are oversaturated. How does the picture look in real life, on the screen? Fantastic! Skintones are spot on, and WOW, the colors look beautifully accurate and have good POP. I’ll explain more below.




How do you do this? Open up the saturation windows and use the 75% saturation window patterns for calibrating, instead of the typical 100% saturation windows. Here is a walkthrough:

Calibration Walk-through
Hardware:

Colorometer (I used the Display One LT when performing calibrations for this guide, and have since upgraded to an i1pro. All of the suggestions in this method still apply)

Download the ColorHCFR software:
http://www.avsforum.com/avs-vb/showthread.php?t=983943

Laptop or PC close to the screen

Tripod (to hold meter)

Blu-Ray Source settings:

Turn off any picture enhancement modes (sharpness, contrast, dynamic…)

If you are going to use 24fps for viewing, turn this on

Projector Initial Settings:

Color mode: Natural (yes, this matters. Do not use the Theater Black Modes)

Turn off any Frame Interpolation.
Iris: Off (Can be turned back on after calibration is complete)

Choose either low or high lamp mode, but don’t switch during calibration session. You will need a separate calibration for each mode if you are going to use both high and low lamp mode. (This only impacts the grayscale, so that’s all you need to adjust for each mode)

Color = -10 (this gives a good starting point)

Tint = -4 (this gives a good starting point)

Color temp = 6500K, or 6000K

Skintone = 0

You can turn on 2-2 or 4-4 pull down if the Blu-Ray player is set output 24fps

HDMI expanded (Depends on Blu-Ray player setting for Blacker Than Black and Whiter Than White setting)



1) Brightness = Set by eye with AVSHD pattern

2) Contrast = Set by eye with AVSHD pattern (I typically bump my contrast down two to four notches from what the test pattern would suggest. I had problems with overdriving the bulb when adjusting to meet the test pattern. This does sacrifice some lumens though)

Greyscale Calibration

3) Adjust grayscale using the gray window patterns on AVSHD (I use the 90% and 30 or 40% gray windows) You typically don't mess with Green, unless you have to. Only adjust Blue and Red to match Green. Use Gains first with the 90% window, and get the red, green and blue levels equal. Then use the Offsets to adjust the 30 or 40% window, again making red green and blue equal. You may have to go back and forth a few times between the 90 and 30 window to get the correct setting. Remember, gains first on the bright windows, then offsets for the darker windows.


4) Recheck brightness and contrast, and adjust as necessary. Sometimes, adjusting the Gains and Offsets can impact the correct brightness and contrast setting, particularly brightness.

Gamma Calibration

5) Adjust gamma. Use the Custom Gamma. My spreadsheet below helps with setting custom gamma.

My Excel Download

For this, I recommend using my spreadsheet. Instructions on how to use the spreadsheet are in the first post of the thread in link to below. I've attached a copy of this file at the end of this post as well. This spreadsheet has been a HUGE help for me. I developed it because I was tired of constantly calculating the correct gamma brightness, and also the primary and secondary color locations, and brightness. To use the spreadsheet, you copy and paste data from HCFR into the excel spreadsheet. It provides charting, target locations for colors and brightness, dE calculations... For your initial calibation, you only need to use the "Calibration Aid" tab. Here is the link:

http://www.avsforum.com/avs-vb/showthread.php?t=1111066


Go to the Calibration Aid tab. Enter the measured Y value of your 100% Gray window from HCFR. See the pictures below:




Then, using the custom gamma sliders in the EPSON, adjust your Gray windows brightness to match the target Y values (cells N14 thru N24). You will need to adjust the gamma sliders for the 10%, 20%...90% windows. I start with the 90% window, and adjust that, then go to the 80% window and so on until I finish with the 10% window. Some gamma sliders impact more than one brightness window(especially the sliders to the far right), some only impact one (sliders to the left). The sliders on the left affect the darker windows, while the sliders on the right adjust the bright windows. Don't touch the first or last slider! (they impact your 0% grey, and 100% grey, which is brightness and contrast which you've already set)


Alternatively, I’ve included a table that shows the %Y for each gray window, shown below. (this is more work than my spreadsheet, but the table is provided in case you don't have Excel) For instance, the 30% gray window should measure 6.91% of the 100% gray window. If your 100%Y reading is 20 cd/m2, then the 30% window should read 1.38 cd/m2. This needs to be repeated for the 10-90% windows. Do NOT adjust the 0% or 100% window. (the first and last gamma slider bar). I like my gamma to be 2.22 for all windows except the 10% window, which I like to have at 2.15 gamma to improve shadow detail and prevent black crush.

 

 
Code:
Code:
Gray Window\tRelative to  100% Y
0%\t          0
10%\t          0.60%
20%\t          2.81%
30%\t          6.91%
40%\t          13.08%
50%\t          21.46%
60%\t          32.17%
70%\t          45.30%
80%\t          60.93%
90%\t          79.14%
100%\t          100%
6) Adjust Color Gamut


I go in this order. Red, Green, Blue, Yellow, Cyan, Magenta.

Example of 75% saturation Window




Here are the x, y locations and %Y for each color at 75% saturation.

 

 

 
Code:
Code:
\tx\ty\tRelative to  100% Y
Red\t0.5582\t0.3298\t0.213
Green\t0.3032\t0.5323\t0.715
Blue\t0.1907\t0.1273\t0.072
Yellow\t0.3927\t0.4612\t0.928
Cyan\t0.2466\t0.3288\t0.787
Magenta\t0.3189\t0.1979\t0.285
White\t0.3127\t0.3290\t1.000
If you use my Excel spreadsheet, in the Calibration Aid tab, it will make it easier because the target brightness is also shown. When you adjust saturation on the Epson, the brightness will change. As you increase saturation, the brightness will go up and vice versa. Be aware of this. Your goal is to hit the x, y locations for the 75%, and the correct Y. For example, let’s say your 100%Y reading is 25 cd/m2, then Red should hit 5.33 cd/m2 and Green should hit 17.88 cd/m2, and so on. You need to calculate the Y for each color. My spreadsheet does this for you automatically if you enter the 100% Y value.

Special Hint!

I have found a very easy way to hit the correct color locations. This takes away the headache of trying to hit x, y locations (as shown above) and how you adjust saturation and hue to get there. See the red, green, and blue bars in the HCFR picture above? (three pictures back) In the picture, the bars show 98%, 100%, 100% to the left of the ftL and cd/m2 readings. These are the bars I'm talking about. Here are the target %'s for the red, green, and blue bar for each 75% color saturation location. (They are also listed in my Excel spreadsheet on the "Calibration Aid" tab as shown a couple of pictures back).

 

 

 
Code:
Code:
\t             Red Bar Green Bar Blue Bar
Red Primary\t       378%\t24%\t24%
Green Primary\t       15%\t133%\t15%
Blue Primary\t       64%\t64%\t555%
Yellow Secondary      106%     106%     17%
Cyan Secondary\t       24%\t120%\t120%
Magenta Secondary      247%\t41%\t247%
For example, lets say you want to calibrate red. To hit the correct saturation, all you have to do is increase or decrease the red saturation slider in the Epson RGBCMY menu until the red bar reads 378%, and the Green and Blue bar read 24%. If the green and blue bars are not equal, use hue to correct this. Hue is always used to balance colors. When calibrating blue for example, you want green and red to be equal. This creates the correct hue. When adjusting a secondary color, like yellow for example, you want an equal balance of green and red. (red and green will have a high %, while blue will be low.)


Keep in mind that you still need to set brightness (Y) for red, and all the colors The target value will be shown in the "Calibration Aid" spreadheet, or you can calculate it based on the 100% gray window. Remember, calibrate red, green, and blue before you calibrate the secondary colors.

Finished!

That’s it. You’re done! Enjoy. You will notice that your 100% colors are oversaturated, but your brightness at these locations will also drop. (I'll write up some more on this later) This helps compensate for the oversaturation. I have found this method to look far superior to the standard method of using the 75% or 100% Brightness Color Windows. If the Epson CMS worked 100% accurately, we would not have to use my method. You could use the standard method.

Appendix

O.k., so I mentioned that I would explain the brightness drop at 100% saturation, and why this is a good thing. The error in a color (Delta E, or dE) uses saturation, hue and brightness in it’s calculation. This means that if a color is oversaturated, you can use a lower brightness to fool the eye into thinking the color is less saturated. This works, but there are limits.


As you can see from the results above, when you use my 75% saturation technique, the 100% locations are oversaturated. What does the brightness of each color do as you increase saturation from 0 to 100%? Look at the picture below. It stays well behaved up to 75%, but then drops at 100%. This drop in brightness helps compensate for the oversaturation. This is why the 75% method provides a picture superior to the standard calibration method even though the 100% points are oversaturated.



Dan

 

 

 

Gamut, Saturation, Brightness, dE Chart.zip 376.2724609375k . file
 

·
Registered
Joined
·
1,347 Posts
Discussion Starter · #2 ·

Keep in mind that the before and after photos below were from calibrations with an i1D2 meter, which wasn't reading perfectly at the time.  I don't have photos from calibrations from my new i1Pro meter, but I can say that they look even better.

 

edit 4-10-09 Added the photos below to help keep this thread organized with the important data towards the beginning...


They say a picture is worth a thousand words...

 

 
Quote:
Originally Posted by Ph0n33z
Sorry about the confusion. I was looking to see a comparison between Out of the Box PQ and either 100% or 75% in the same mode. (Otherwise the comparison wouldn't be very accurate, no?) In other words, I am interested in seeing what kind of difference there is after calibration compared to how it arrives from the factory. I hope that makes more sense!

I got all of these pictures off the internet after searching for pictures that are used to show color accuracy. I loaded them onto my PS3, which is my Blu-Ray player.


Here you go. I see that my camera added a little warmth (red push) to the pictures, which I noticed in the picture of the little girls and fleshtones mostly. This is not the case in real viewing, but all pictures are taken with the same settings, so they all have the same warmth from the camera. First picture in each comparison is my 75% method. Second picture is the default Natural Mode. There is ABSOLUTLY NO DOCTORING OF THESE PICTURES. I can provide the originals if requested. I simply resized them(1600x1200 to 1024x768), and sharpened them (because my camera wasn't focusing properly, and resizing softens pictures). All done in Infranview. Camera is an older Canon A60 2MP set to manual mode, on a tripod. F 4.5, exposure 0.8 seconds for all. Color mode on camera was daylight mode, no flash of coarse.


For the Default Natural Mode: (natural is the most accurate color mode)

Brightness: 1 (same brightness as used in my 75% method)

Contrast: -2 (same contrast as used in my 75% method)

Color: 0

Tint: 0

6500K color temp.

Skintone 3

RGB and RGBCMY all set to Zero.

Gamma set to 2.2 preset

Low lamp mpde (same as used in my 75% method)

Auto Iris off (same as used in my 75% method)


My method:


Default:




My method:


Default:




My method:


Default:





My method:


Default:




My method:


Default:



A couple of example shots with my method:




Attached is the HCFR file from the "My Method" pictures.


Dan


Here are a couple more examples of my Epson projector calibrated using the standard calibration method, versus my 75% saturation method.


If you perform all 30 saturation window measurements in HCFR, you can see these plots. Go to Measures>>>Saturations>>>All Colors. Use the saturation windows in the AVSHD as I showed above.


See the two pictures below. Both curves in each picture show the error in color. The X axis is % saturation, and the Y axis is error. The top curve shows the error in saturation. If the line isn’t at zero, then it is either oversaturated (above the zero line), or undersaturated (below the zero line).


The bottom curve in each picture is the error in Hue. These curves do not include error in saturation or brightness. It only looks at whether the color has the correct mix of red, green and blue. The goal is to stay below six, and more preferably below three.


Here is the chart for the standard method of calibration using 75% or 100% Brightness, 100% Saturation windows.





Here is the chart for my method of calibration, using 100% Brightness, 75% Saturation windows




Pretty amazing huh? Using the standard calibration method, the color saturation error and hue error is excellent at 100% saturation (the outer edge of the color gamut)… but what about colors inside the gamut? Horrible! Very undersaturated, and hue isn’t the best either (especially red).


Looking at the second picture, using the 75% saturation method, look how excellent everything looks up to 75% saturation. This area makes up a very large part of the color gamut. Saturation error and hue are excellent. Things get oversaturated at 100%, but like I stated earlier, the drop in brightness at 100% color helps compensate.



Dan

 

 

 

4-9-09 75% Saturation.zip 4.4404296875k . file
 

Attachments

·
Registered
Joined
·
775 Posts
Hey Dan, you ought to include somewhere that %75 saturation HCFR reference file you made. That has make it a TON easier when doing x,y positions trying to hit 75% sat. (I know it's in the spreadsheet, but you have a realtime color point in HCFR!!)
 

·
Registered
Joined
·
539 Posts
Excellent stuff Dan!


You just gave me an excuse to once again do some more calibration.


Will try it out soon. Feedback will be given if appropriate.
 

·
Registered
Joined
·
1,347 Posts
Discussion Starter · #5 ·

Quote:
Originally Posted by cbaseuser /forum/post/16169443


Hey Dan, you ought to include somewhere that %75 saturation HCFR reference file you made. That has make it a TON easier when doing x,y positions trying to hit 75% sat. (I know it's in the spreadsheet, but you have a realtime color point in HCFR!!)

Got it in there now. Thanks for the suggestion.


Any additional input or suggestions are welcome from all.


Dan
 

·
Registered
Joined
·
228 Posts
Dan you are the man! This is exactly what I was looking for. This and your spreadsheet are fantastic aids. Any suggestions on how best to adjust the CMS? By that I mean if x is off adjust hue if Y adjust sat etc? Based on your earlier PM to me it sounds like you can watch a live view of the CIE in HCFR and use that as a visual aid also correct? Any screen suggestions for the Epson's? Thanks again.
 

·
Registered
Joined
·
1,347 Posts
Discussion Starter · #8 ·
rwestley, much appreciated.


doug goldberg,


If you look at the color gamut, just remember that saturation moves you in and out from the triangle, and hue basically spins you around the triangle.


It's hard to generalize with x, y and how they impact saturation and Hue.


Red is probably the easiest though. x will impact saturation (higher x means more saturation). y will change hue.


Cyan: x will impact saturation (lower x means more saturation). y will change hue.


Green: y will mostly impact saturation (higher y means more saturation). x will mostly impact hue.


Magenta: y will mostly impact saturation (lower y means more saturation). x will mostly impact hue.


Blue and yellow are mixed mostly mixed with what x and y do.


...and yes, in HCFR if you have the continious measure on (green play button), and you go to the CIE Diagram (gamut chart), your measurement point will show up as a yellow dot. The only problem is that the 75% locations are not shown on the gamut chart in HCFR.
It can still be useful to see how saturation and hue move the color though.


Dan
 

·
Registered
Joined
·
149 Posts
stereomandan,


Bill Mitchell pointed this out to me in separate post. It is worth adding I think to the checklist, when running the final report.

Quote:
By the way, if you are using the technique to measure the colors at 75% stimulus, you would be better off measuring the grayscale and the primary/secondary colors separately; that way HCFR will measure the 75% stimulus white at the same time as it measures the 75% stimulus colors. When you press its button to take all the measures at once, it inserts the grayscale 100% white measure as the white value in the color grid, which makes the delta E/delta luma entries in the primary and secondary color grid misleading.

Hope this helps and is it of use to you. I think it is a good point as I normally run the whole thing together, what do you think?
 

·
Registered
Joined
·
1,347 Posts
Discussion Starter · #11 ·
smallpooldad,


Thanks for the suggestion and what you say there is true. However, I don't use, and don't recommend using the 75% stimulus(Brightness) patterns on the Epsons. I've done measurements, and the 100% stimulus and 75% stimulus patterns give nearly identical results for the location of the primary and secondary colors. Using 75% stimulus windows just make it that much harder to figure out the correct brightness for all the colors.


If you run a full set of saturation measurements, you end up running the 100% stimulus patterns anyway.(at 0%, 25%, 50%, 75% and 100% saturation) This is under Measures>>>Saturations>>>All Colors. You then use the saturation windows that I point out above. This way you don't have to worry about the greyscale measurement, because everything is referencing 100% stimulus.


Most of the time, all I run are a full set of grayscale measurements, and the full set of saturation measurements. This gets you all the information you need.


You use 75% stimulus windows when a projector has a hard time with the 100% stimulus windows (like older CRT's and even some newer projectors(the JVC RS20 in custom user color modes)). Fortunately, the Epsons are good in this regard.


Dan
 

·
Registered
Joined
·
149 Posts
stereomandan,


Interesting point, different from Bill's.


So when I recalibrate next, late next week, I will look at two files, a bit more work but it will give me a visual idea of what you wrote and he wrote.


Until then thank you for all the help and guidance.

On a "light" note;

"In the beginning there was nothing. God said, 'Let there be light!' And there was light. There was still nothing, but you could see it a whole lot better."


Ellen DeGeneres, (attributed)

US comedian and actress


"But was it 100% light, 100% saturated light, 75% light, or 75% saturated light?"

Attributed to me after reading too many posts on avsforums.com and drinking 12 beers during a calibration session.

Correction 12 organic ales.
 

·
Registered
Joined
·
1,347 Posts
Discussion Starter · #13 ·
That's funny.
mmm beer. Cheers!


Bill Mitchell doesn't have an Epson projector, so he is giving you advice based on other displays. If the Epson had problems with 75% and 100% stimulus(Brightness) patterns, I would also recommend what he suggests. Fortunately, the Epson is good in this regard, so it just makes things easier to use 100% stimulus patterns.


Just to be clear, the "Saturation Windows" all use 100% stimulus, so when you run all 30 saturation measurements, you end up running the 100% stimulus, 100% saturation patterns in the process.


This is identical to running the "100% Windows" seperately.


Dan
 

·
Registered
Joined
·
149 Posts
stereomandan,


Ok, understood and agree.


Well I could not wait till the end of next week to get this done, so after the wife went to sleep last night, I calibrated (no beers).


The "Saturation-Luminance" chart was un-bloody believable, after saturation measures were run; straight as an arrow an all time first, but only adjusted brightness in RGBCMY. The gamut performance on the CIE was also remarkable, no bendies except a tiny bit in cyan. It was very late and I did not get time to adjust the hues and saturations. Will do this tonight, but still a remarkable method using your spreadsheet, you are to be congratulated.


The only problem I encountered was that my setting for Gamma was 2.0 and came in nearly dead on straight at 2.25. When I tried to adjust with the custom menu by moving the points up slightly it came in at 2.5!, so I had to move all the points a lot higher to get it back down - weird, but it was taking too long so I left it for tonight. I moved it back to 2.0 giving 2.25.


I might just have to go with that if I cannot bend the gamma back properly before setting the hue and saturation. I believe, but am not sure, the most likely reasons for this is, in order of likelihood are:



1. That throw maybe too close (too late to change) at 11'9". Making the ftL above 12.2 so harder to get perfect numbers as some say one needs to be below an ftL of 11.0

1.a On the good side the Y is 41.62 and as the Epson 6100 (140 hours) dims this should solve itself.

2. It might also be due to the LCD panel being organic, but that I really know nothing about, versus inorganic for the 6500UB.

3. Obviously the Epson 6100 is different from the 6500UB so maybe at these very extreme points(2.0 Gamma setting and too close at 11'9") it does not calibrate quite as well.



Should I then plug in Gamma as 2.25 on the spreadsheet if I cannot bend it correctly, or should I adjust the hue and saturations based on 2.22, hoping they will move the target down to 2.22? I believe the color was at -5, and tint at 0 or -1, I'm not near the PJ now, would that have any affect?


In HCFR they state in their help section that in a very dark room, which mine is as it has virtually no ambient light other than the color of the room itself, that a Gamma of up to 2.5 is acceptable, so should I just forget about battling Gamma down to 2.22 and just work off 2.25? My personal feeling is to leave it, as I believe the ageing of the lamp will solve the issue and the line is pretty straight on at 2.25. If so should I set the reference gamma in HCFR under "Preferences" at 2.25?. If you do agree with leaving it at 2.25 what would you think would be a good Gamma number at 10%?


Last question, do you know what the far left and right points on the custom gamma chart do? They are adjustable so one must assume they serve some purpose. I cannot find any posts that explain this on avsforums, may be nobody knows for sure.


Other than the Epson Gamma adjustment issue all went well so far. If I get it done tonight I will post it.


Thank you it seems to be going great.
 

·
Registered
Joined
·
1,347 Posts
Discussion Starter · #15 ·
Thanks!


To me, 2.5 gamma is way too dark and doesn't look natural. 2.25 is so close to 2.22 that you shouldn't even worry about it.


The far left and right points on the gamma curve would end up adjusting brightness and contrast. Since you already set this properly in the main menu, there is no reason to change the first and last slider.


Just be aware that the saturation-luminance curves in HCFR are all screwed up. In order to get accurate saturation-luminance curves you need to input the data into my spreadsheet. The saturation-shifts charts are fine in HCFR. In order to copy and paste data from HCFR, click the "Editable data" tab. Then you can hightlight the numbers you want, then copy and paste into my spreadsheet.


When you end up doing your color saturations and hue the saturation-luminance curve might change, but that's o.k. as I explained above.


Dan
 

·
Registered
Joined
·
149 Posts
Found these all on the same page:


"HCFR's gamma settings are unnecessarily complex. Do you have it set to Display Gamma in Advanced, Preferences, References? If you don't, then set it that way. If you do, then I am at a loss as to why you prefer a 1.9 gamma. Assuming that your black level is set correctly, I have never seen display with a gamma that low that offered optimal performance. Most users will find 2.2-2.35 to be the most subjectively pleasing tradeoff between shadow detail and image depth."

__________________

Tom Huffman

Rockville, MD


"Gamma is very important and unfortunately very tricky. The most important part of the gamma curve is the lower 10% and the ability to measure it at that level is a problem. For example, you can have an accurate curve of the other 90% and poor performance in the last 10% and it will wreck the image."

__________________

W. Jeff Meier


"Very true, I feel gamma is very important. It provides the overall tonal quality of the image. This can be the end all or be all for a film director trying to achieve the correct atmosphere within a film.


I’ve sacrificed slight shadow detail, by allowing a slight amount of black crush, to obtain a ruler flat gamma line of 2.2.


I suppose an analogy is to Hi-fi. Are you willing to sacrifice a good midrange performance for a more detailed treble output? Personally, I would always prefer to get a more natural accurate midrange."

______________________

delphiplasma



"Gamma is very important.


I think it's unfortunate, however, that the ISF is telling people that the reference gamma is 2.2 when it is not. Now we have a whole generation of people doing calibrations who assume 2.2 to be the target."


"Also keep in mind that a gamma this low can make very dark scenes really 'pop' (inaccurately, but it can still look very impressive). What you should be looking at at the same time though, is how much contrast and how washed out and flat bright scenes will become with such a low gamma. This is why when tweaking gamma down a little bit for subjective reasons, while you may be doing so to improve subjective performance down low, the damage is being done in brighter images and that's where you want to be careful to make sure you're not making everything thats brighter look pasty and flat.


And of course, watch for a little while before making rash judgements. Any time you take a TV out of a calibrated mode and right into vivid or something, everyone will probably say OH WOW!!!! But after a while, and going back and forth and learning to appreciate an accurate image, few would agree with that quick and rushed judgement."


ChrisWiggles


Link:

http://www.avsforum.com/avs-vb/showthread.php?t=1053845


Any opinion, seems reasonable?
 

·
Registered
Joined
·
149 Posts
Thank you for the reply.


Well the half-German side of me wanted 2.22222222222, you know the bomb must drop precisely within 1mm of the target. The half-Russian side of me says who cares so long as it does the job have another vodka, so I will go with you and the Russians.


I liked that side of the family better anyway.
 

·
Registered
Joined
·
539 Posts
Now we are talking... (about gamma)



Have spent a few hours now preparing for a 75% saturation calibration, but instead I've been doing the gamma over and over again... that nasty little thing is a slippery one...


Reading Dan's guide again, with a set of tired eyes, I might actually have understood how you guys adjust gamma. Using the spreadsheet and the 10% IRE patterns, you are basically adjusting gamma in realtime to its "spreadsheet position". Am I correct?


Up til now I have adjusted, done a greyscale, analysed gamma, slight new adjustment, do greyscale, analyse gamma... painful stuff.


Good stuff guys!
 

·
Registered
Joined
·
1,347 Posts
Discussion Starter · #20 ·
Yes, my spreadsheet will give you the target brightness (cd/m2) for each grey window based on your 100% brightness reading. You enter the 100% brightness reading from HCFR into the Excel spreadsheet cell I1 and the spreadsheet will calculate the brightness that each grey window should be in cells C15 to C23.


I have a procedure I use for gamma with my Epson that is very easy. I'll try to write it up and post it tomorrow.


I have found that once you adjust greyscale, you don't need to mess with it again when you adjust gamma. (as long as you don't touch the first and last slider in custom gamma)


Dan
 
1 - 20 of 749 Posts
Top