Reading and interpreting calibration charts and data for dummies - Page 4 - AVS Forum
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post #91 of 181 Old 09-16-2005, 11:47 AM
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Thanks for the explanation - that was the answer we were looking for. Sounds like it does make more sense for the option to default to OFF - we got thrown for a loop because it defaulted to ON!
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post #92 of 181 Old 09-16-2005, 01:23 PM
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Same here - thanks Mark!

Jeff (aka umr ), does your software do the same thing? That is, if everything is at 100% then I hit the target?
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post #93 of 181 Old 09-16-2005, 01:59 PM
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Quote:
Originally Posted by krasmuzik View Post

Thanks for the explanation - that was the answer we were looking for. Sounds like it does make more sense for the option to default to OFF - we got thrown for a loop because it defaulted to ON!

So Mark is saying grayscale wise it doesn't matter whether it's off or on. But for true CIE readings it needs to be off.

I didn't see that link on the internet that Mark said would pop up during Cedia, the link for the free CF upgrade? I have the Accupel coming next week am I'm going to run into any hookup snags as is or with the upgrade with my laptop? Right now I have both sensors (1eye/trichromat) accessible in the directory.

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post #94 of 181 Old 09-16-2005, 03:11 PM
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Quote:
Originally Posted by maxleung View Post

Same here - thanks Mark!

Jeff (aka umr ), does your software do the same thing? That is, if everything is at 100% then I hit the target?

Yes.
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post #95 of 181 Old 09-18-2005, 04:54 AM
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This has been a very informative thread and it got me thinking about how calibration must keep up with new technologies.

Genoa ColorPeak and TI's BrilliantColor are expanding the color gamut that the displays that are using this technology can produce.

How does a calibrator accurately handle these new display technologies?

Here is Genoa Color's explanation of their technology.

Pardon me Bob if I'm too off topic with this question, but I think it is relevent enough to benefit all of us.

Steve
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post #96 of 181 Old 09-18-2005, 11:20 AM
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hex gamuts rather than trigamuts are certainly interesting from a research point of view.

But wide trigamut has not even been accomplished for HDTV - which is barely an improvement over SDTV - so you can forget about hex gamuts for a long time.

A display composed of a hex gamut - only adds complexity and unused capability to the display - as long as there is no software to drive it.

All media currently is either RGB or YCbCr - which is a trigamut. The source media and interconnects would have to entirely change throughout the industry if hex gamuts are to be adopted for more than making pretty pictures.

What they will do is add more calibrator challenge if there are no controls to put the colors back where the HD/SD standards say they should be. The calibrator will leave and you will still be left with an unnatural looking picture.

So until the display manufacturers get it together with the broadcasters and filmmakers - they are doing nothing more than colorizing the picture. Which is nothing new - their marketing departments have always operated on the mistaken idea that "different" means "better".
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post #97 of 181 Old 09-19-2005, 05:07 AM
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Thanks Kevin,

I see, the improvements of video will have to be industry wide, from source to display for best results, and with that will be standards for calibrators to reference to.

It looks like companies like Genoa Color are getting the ball rolling by bringing to market a method of taking existing input RGB or YCbCr data and transferring this information through a multiple primary converter (post processed), resulting in a widened gamut.

Based on the Genoa Color White Paper, I assume there would be no difference in the way a calibrator would calibrate this type of display.

I guess it reminds me of Dolby creating 5 channels out of only 2 channel sources. Not the ideal compared to 5 discrete channels, but does create a relatively believable soundstage.

Steve
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post #98 of 181 Old 09-19-2005, 11:10 AM
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Not the same thing as Dolby ProLogic. Dolby Prologic encoded the extra channels using 'inaudible" phase differences into stereo - which then extracts extra channels. This is actually rather similar the way that color was added to B&W TV signal.

Adding more colors is not the same thing as adding more audio channels! Rather adding more colors is more like a manufacturer enforced audio equalizer setting - does not sound so attractive anymore does it?

It will take more than a startups white paper to change the entire video industry. YCbCr is only a media compression format - it is not a camera and display format. That is a major problem to change considering that someone would have to invent cameras/displays that are not native RGB.

Just look how long HDTV is taking - ten years from release and ten years in development. And that includes a wide gamut HDTV standard that expands the trigamut to more saturated colors all the way around - that was never adopted.


The only issue for calibrators is having the controls to calibrate back to the standard tri-gamut - which means the expense of the "enhancement" is wasted - just like when you buy an audio equalizer only to set it to neutral. The problem is getting color point controls for calibrators often does not happen even now - with oversaturated primaries or yellow segments.
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post #99 of 181 Old 09-19-2005, 11:16 AM
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The genoa paper does not post the 5P primary values - but let me guess from the charts. I will post my zoomed color target so you can see how far they are off from the standard.
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post #100 of 181 Old 09-19-2005, 12:58 PM
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Here are the perceptual charts based on Genoas white paper. I posted here as it gives me a chance to add some review words to my charts - maybe making them more understandeable.

krasmuzik GENOA

They first propose a Wide Gamut - the advantage here is that gamma is not changed because Cyan is a deeper towards Blue and thus you do not get brighter Whites - but Cyan gets an F---

The natural greyscale point defined by the RGBCY primaries is thus grossly blue - give it an F---

But that means Magenta is deeper towards Blue as well - give it a D-

Green is deeper and more Cyan - give it a D+

Blue and Yellow are just a bit overdone - give them a B. Red is overdone - give it a C (note many display like Sim2, Infocus SP7210, Optoma H79 are similar reds)

So if you were watching an HD source on this gamut - the picture would look very strange. Especially skies and grass - it would look like these SciFi shows that colorize things to make it look like another planet.

But Genoa realizes that and have a High Bright gamut - which is closer to HD spec.

The Red is a less pale Orange - causing Magenta to be pale as well - combined with a paler Blue. Give them all a B - but you can see they made the dark colors pale because it improves brightness.

The lighter colors Cyan, Yellow, and Green - they have oversaturated a bit - because Cyan and Yellow are used to create white they can afford to do this with the brighter colors. The hues are pretty good - also give them a B.

As a result the greyscale is not bad - give it a B+ for being just a bit Cyan.

I have seen worse color/greyscale points on other projectors - as a calibrator though I strive for an A - as I can see the difference to the point of annoyance. I would consider a B projector OK if you don't care about videophile stuff and are budget limited, but only an A projector would be highly recommended.

You can see the compromise in the gamma. The gamma curve is higher value and the blacks are crushed (or whites are popped depending on your viewpoint). I would give gamma a B as well.


So bottom line - the real point of these CMY colorwheels is to improve brightness - at the expense of a videophile calibration on greyscale/colors/gamma. In other words the usual game - market the big numbers - not the videophile numbers. Using them for wider gamuts makes little sense - no brightness improvement - but wierdly pushed colors for HD sources.
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post #101 of 181 Old 09-19-2005, 01:18 PM
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Quote:
Originally Posted by gregr View Post

But something is clearly wrong on the chart at the start of this thread. The yellow measurement is outside the line between the green and red measurements, and that is physically impossible unless the projector has special processing to adjust the primaries separately from the complementary colors, and the 7210 doesn't have that type of processing.

Greg,

The ScreenPlay 7210 does use color correction processing to independently correct for primaries, secondaries, and white point. The corrected yellow indeed does not lie directly between the green and red primaries when viewed on a CIE 1931 chart like the one at the beginning of this thread. This non-triangular gamut is intentional.

Some people say we are "cheating" because we choose a yellower green than some others do, however the reason behind this choice is to preserve contrast. Adding yellow to the green moves the white point to a warmer temperature. If you turned off all processing, the natural white point in the ScreenPlay 7210 would be very close to D65. Because of this, you lose no contrast when you properly setup your projector for 6500K. Based on all of the feedback I have been able to gather (as well as my own personal preferences), this boost to contrast is more important to relative picture quality than the absolute saturation of green.
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post #102 of 181 Old 09-19-2005, 04:05 PM
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Quote:
Originally Posted by Bob Williams View Post

Greg,

The ScreenPlay 7210 does use color correction processing to independently correct for primaries, secondaries, and white point. The corrected yellow indeed does not lie directly between the green and red primaries when viewed on a CIE 1931 chart like the one at the beginning of this thread. This non-triangular gamut is intentional.

Thanks for the info Bob. I didn't see anything about user adjustable primaries and complementaries in the data sheet so I figured it had no capability for this kind of independent color correction. If it does have user control over the primary and complementary colors please confirm that.

I've never measured a 7210 but this will keep me from tearing my hair out puzzling over what happened to the yellow measurement if I ever do.

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post #103 of 181 Old 09-19-2005, 04:09 PM
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Bob,

"Based on all of the feedback I have been able to gather (as well as my own personal preferences), this boost to contrast is more important to relative picture quality than the absolute saturation of green."

Not to be a curmudgeon, but why then hasn't Infocus used an adjustable or dynamic iris to get more of that desirable contrast?

Noah
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post #104 of 181 Old 09-19-2005, 05:15 PM
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gregr

If you get BobWilliams to divulge any supersecret service codes - I want in on them . The accessible service menu only has the typical ADC YPbPr controls and only for HD - not 480i.

Even if it was NEC HT1100 style primary/secondary control of sliding along the triangle over to the next secondary/primary is something - though not as good as insanely more expensive projectors.

All of the ScreenPlay's I have measured have always had perfect hues on secondaries - I just want to try some tricks....
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post #105 of 181 Old 09-19-2005, 06:55 PM
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Quote:
Originally Posted by noah katz View Post

Bob,

"Based on all of the feedback I have been able to gather (as well as my own personal preferences), this boost to contrast is more important to relative picture quality than the absolute saturation of green."

Not to be a curmudgeon, but why then hasn't Infocus used an adjustable or dynamic iris to get more of that desirable contrast?

The optical design in the ScreenPlay 7210 is at its maximum contrast already, so no additional iris will make it any higher.
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post #106 of 181 Old 09-19-2005, 08:11 PM
 
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Welcome back to the high dollar forum Bob!! I haven't seen that smiling face for a while. I thought you quit the forum from being brain fried from all the questions. I see you frequent the "other" forum.

Scott
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post #107 of 181 Old 09-30-2005, 02:15 PM
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good one for calibration forum
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post #108 of 181 Old 10-04-2005, 06:36 AM
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Quote:
Originally Posted by krasmuzik View Post

As long as a few dummies post - then the subject is still valid

At this point I am too dumb to read further into this thread. While the math is not beyond me, some of the discussion is not being followed do to the condition that as a dummie I do not always 'get it' and the lack of layman discussion only serves to white-out my comprehension.

When will D* stop pushing HD-Lite while charging us for full HD? Digital input on a CRT is a reality, not a possibility.
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post #109 of 181 Old 10-04-2005, 02:25 PM
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Originally Posted by TheFerret View Post

At this point I am too dumb to read further into this thread. While the math is not beyond me, some of the discussion is not being followed do to the condition that as a dummie I do not always 'get it' and the lack of layman discussion only serves to white-out my comprehension.

A fair point. Where did you get lost?
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post #110 of 181 Old 10-06-2005, 09:42 AM
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A fair point. Where did you get lost?

I must be dumber than Ferret, because I got lost off of the initial question posed in this thread....

Are the Primary (squares) on Bob's chart measured from his equipment or are they just a predetermined ideal?

What would a theoretically perfect chart look like? An equilateral triangle with white directly in the middle and the secondaries bisecting each line between primaries?

These are the type of dummy questions I need answered so I can even gain a limited understanding of these charts.
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post #111 of 181 Old 10-06-2005, 10:13 AM
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Quote:
Originally Posted by Mike__P View Post

I must be dumber than Ferret, because I got lost off of the initial question posed in this thread....

Are the Primary (squares) on Bob's chart measured from his equipment or are they just a predetermined ideal?

What would a theoretically perfect chart look like? An equilateral triangle with white directly in the middle and the secondaries bisecting each line between primaries?

These are the type of dummy questions I need answered so I can even gain a limited understanding of these charts.

The squares are the target values (not measured) for each color and the triangles are the measurements except for white which is a black box with an asterisk in it. The measured primaries, secondaries and white would ideally be on their target values.
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post #112 of 181 Old 10-06-2005, 10:33 AM
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Originally Posted by umr View Post

The squares are the target values (not measured) for each color and the triangles are the measurements except for white which is a black box with an asterisk in it. The measured primaries, secondaries and white would ideally be on their target values.

So here is a follow up dummy question...How are the targets determined? Are the targets based upon what chart you are looking at, ie CIE1931?
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post #113 of 181 Old 10-06-2005, 10:46 AM
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Quote:
Originally Posted by Mike__P View Post

So here is a follow up dummy question...How are the targets determined? Are the targets based upon what chart you are looking at, ie CIE1931?

The color of each primary, secondary and white is set by the appropriate standard. Note the reference to the HDTV standard on the plot. They each assign an xy coordinate that is plotted on the CIE1931 chart. The type of coordinate system (CIE1976...) will change the plot, but the target color will remain the same.
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post #114 of 181 Old 10-06-2005, 10:57 AM
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Thanks Jeff, I think I am starting to get the jist of it, sorry to dumb down the thread.
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post #115 of 181 Old 10-06-2005, 11:04 AM
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You might want to go to my website and download the documentation for my software. It provides significant information on how to measure and calibrate a display and along with links to other resources on the web.

www.accucal.org (look under i1 Pro DCS software documentation)

Good Luck! This can be pretty fun once you figure out what is going on, but the climb can be a little steep.
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post #116 of 181 Old 10-06-2005, 11:49 AM
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Originally Posted by umr View Post

You might want to go to my website and download the documentation for my software. It provides significant information on how to measure and calibrate a display and along with links to other resources on the web.

www.accucal.org (look under i1 Pro DCS software documentation)

Good Luck! This can be pretty fun once you figure out what is going on, but the climb can be a little steep.


Will do, thanks again. ps. Your site is timing out for me right now...provider issue? I'll try again later.
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post #117 of 181 Old 10-06-2005, 01:31 PM
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Originally Posted by Mike__P View Post

Will do, thanks again. ps. Your site is timing out for me right now...provider issue? I'll try again later.

You are probably seeing Cogent Communications/Level 3 problems. My web hosting service uses Cogent which is causing some problems at the moment if you are on Level 3. Many Time Warner users are on Level 3. Read the following news report for more information on this.

http://www.theregister.co.uk/2005/10/06/level3_cogent/
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post #118 of 181 Old 10-06-2005, 02:10 PM
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Yep, brighthouse user here, so that explains it.
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post #119 of 181 Old 11-13-2005, 04:38 AM
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Hi,
can anybody explain a dummy in what way can help DeltaE, also dC and dH to make a calibration. I have read the Posts to this issue in this thread but i canĀ“t get the point.

Thanks a lot, rgds Damdy

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post #120 of 181 Old 11-13-2005, 03:28 PM
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Damdy - Delta E is a measure of color error that includes in its definition the amount of grayscale error. That is, if you have the "color" correct (think of the xy plane on the gamut), but you have too much or too little light, then that is the grayscale error component. This is also referred to as "Delta L*".

Think of Delta C* as the color error independent of the amount of light. However, using the 1976 formula, there is still a heavy influence from L* in calculating dC*. With me so far?

Delta H comes into play with the newer versions of Delta E*. Now, you have a much more complex set of calculations with more discrete components. This is essentially the error in hue, or angle from the HSL color space (HSL contains three components: an angle on a plane (hue), the "purity" of the color on that angle (Saturation, or the distance from white), and the amount of light (Lightness). If I understand the issue correctly, humans are very sensitive to changes in Hue, though Poynton dismisses this entire color space in a fairly offhand fashion.

I'll leave it to Kevin to give a more advanced iteration of this last point.

Later,
Bill
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