Grayscale variances - different patterns, plasma calibration - Page 10 - AVS Forum
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Old 03-17-2013, 12:34 PM
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Thank you very much
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Old 04-07-2013, 06:52 AM
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Quote:
Originally Posted by Light Illusion View Post

There has been no single size.
It varies for each display we have profiled.

That is the idea of the procedure - you define the ideal patch size foe any given display.

Steve


ramp method -ideal patch size for any given display -only 3DLUT or good for 1DLUT ?
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Old 05-27-2013, 11:33 AM
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Originally Posted by zoyd View Post

Regarding the "ramp method". If I follow the procedure described the size of a 100% stimulus window that best matches the ramp luminance at the probe position is 5% area. I still think this is too small based on the data above, the only thing it accomplishes is to ensure that the 100% pattern generates an average screen luminance (as measured over a partial screen by the way) that a linear ramp generates. This isn't tied to any physics that I can tell.

Where can I find details of the ramp method, please?

I've been searching in vain through the forum to find more about it.

Thank you.
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Old 05-27-2013, 11:55 AM
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Quote:
Originally Posted by fluxo View Post

Where can I find details of the ramp method, please?

I've been searching in vain through the forum to find more about it.

Thank you.

Hi fluxo, have a look here...


http://www.avsforum.com/t/1441407/grayscale-variances-different-patterns-plasma-calibration#post_22627430
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Old 05-27-2013, 12:00 PM
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Originally Posted by -Hitman- View Post

Quote:
Originally Posted by fluxo View Post

Where can I find details of the ramp method, please?

I've been searching in vain through the forum to find more about it.

Thank you.

Hi fluxo, have a look here...


http://www.avsforum.com/t/1441407/grayscale-variances-different-patterns-plasma-calibration#post_22627430

Thank you for the swift and helpful reply. That's an interesting method, but not quite what I was expecting.

I'm thinking of a different approach. I'm not sure if it's been done before - it doesn't seem terribly un-obvious, but you never know. I will, therefore, probably be back at some point with some patterns to post to illustrate the idea.

Thank you very much.
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Old 05-27-2013, 02:17 PM
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[snip] I've just seen the Chad B pattern set :--)
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Old 05-29-2013, 05:42 AM - Thread Starter
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Quote:
Originally Posted by fluxo View Post

[snip] I've just seen the Chad B pattern set :--)

Heres an intereting article re pattern types and sizes.

http://www.tlvexp.ca/2013/05/apl-of-the-covenant-a-transmitter-for-talking-to-plasma-tv-gods/

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Calibration Management Disc
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Old 05-29-2013, 09:47 AM
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Originally Posted by ndaa75 View Post

Heres an intereting article re pattern types and sizes.

http://www.tlvexp.ca/2013/05/apl-of-the-covenant-a-transmitter-for-talking-to-plasma-tv-gods/

If he would have used the DeltaE u.v. formula, I'm sure the results would have been a lot greater.
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Old 05-29-2013, 09:57 AM
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Originally Posted by cadett View Post

If he would have used the DeltaE u.v. formula, I'm sure the results would have been a lot greater.
\

If the errors in a chart are greater, but still undetectable with the human eye, who cares....
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Old 05-29-2013, 03:44 PM - Thread Starter
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Originally Posted by Wouter73 View Post

\

If the errors in a chart are greater, but still undetectable with the human eye, who cares....

+1

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Old 05-29-2013, 03:50 PM
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This is only for two sets, it doesn't speak for all. I know on the ST60 the difference in measurements are greater. Made me rethink the calibration process on this set.
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Old 05-29-2013, 06:20 PM
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Quote:
Originally Posted by ndaa75 View Post

Quote:
Originally Posted by fluxo View Post

[snip] I've just seen the Chad B pattern set :--)

Heres an intereting article re pattern types and sizes.

http://www.tlvexp.ca/2013/05/apl-of-the-covenant-a-transmitter-for-talking-to-plasma-tv-gods/

Thank you for the link. I've been having a good look at some of these APL patterns. Regarding such patterns, the AVSHD 709 documentation says "these custom patterns intend to hold APL constant for a series of measurements." Some of the AVSHD 709 pattern sets go much further than that. They are, what I would call "permutation patterns". For each pattern in a set of that kind, every other pattern is a pixel-permutation of that. Such pattern sets satisfy much stricter constraints than APL pattern sets in general and are a good choice I think (if you wish, I can explain why I think that is so).

I've been crunching some of the numbers in these pattern files to see if I can find anything interesting. First I found a couple of discrepancies in some of ChadB's APL patterns. Not serious discrepancies, but small APL differences in one of the sets I looked at.

Then I looked at the GCD greyscale APL patterns (10% stim increments). I analyzed them very quickly, so it is possible I may have made a mistake. But at a first glance - and I do sincerely hope I am wrong about this - the pattern set looks like a complete disaster. It is not a true APL pattern set:



Those plots show the variation in APL and average luminance (normalized, various assumptions made) for the patterns in the set. We can disagree on whether or not these differences matter, but if one is going to construct an APL pattern set then, at the very least, the APL should be held constant or nearly so. I'm not seeing that for the GCD patterns.
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Old 05-29-2013, 06:49 PM
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I just checked the 0%, 50%, and 100% patterns and got average stimuli of 18.7%, 19.0%, and 22% respectively. The intent of the GCD APL patterns was to hold the average stimulus constant at 22% (flat line upper graph) so that is not as intended. The bottom graph will be essentially the same either way, which is what what matters for the transfer function variability. Perhaps visca can fix that in the next version.
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Old 05-29-2013, 08:10 PM
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Quote:
Originally Posted by zoyd View Post

I just checked the 0%, 50%, and 100% patterns and got average stimuli of 18.7%, 19.0%, and 22% respectively. The intent of the GCD APL patterns was to hold the average stimulus constant at 22% (flat line upper graph) so that is not as intended. The bottom graph will be essentially the same either way, which is what what matters for the transfer function variability. Perhaps visca can fix that in the next version.

Thank you.

I wonder if you could elaborate on the quoted sentence I have put in bold. I am also interested in how you are checking the APL values. I have some doubts about the method I used. In particular, concerning the way I extracted frames from the MP4 file.

Finally, I would like to say that my "complete disaster" wording was perhaps excessive. It would have been better had I phrased it more moderately.

Cheers.
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Old 05-29-2013, 08:26 PM
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Quote:
Originally Posted by fluxo View Post

Thank you.

I wonder if you could elaborate on the quoted sentence I have put in bold. I am also interested in how you are checking the APL values. I have some doubts about the method I used. In particular, concerning the way I extracted frames from the MP4 file.

smile.gif I just extracted frames from the mp4 file too, which should be fine but we'd need visca to check the originals to verify.

Regarding the transfer function variability I've found that it's quite stable (average gamma values within +/- 0.05) in the luminance range probed with the above values. The only observable differences I've seen in calibrated performance (again gamma, not grayscale/color) has been between using smallish windows where the luminance range is on the very low end (< a few %) vs. APL in the 5-20% luminance range.
Quote:
Finally, I would like to say that my "complete disaster" wording was perhaps excessive. It would have been better had I phrased it more moderately.

Cheers.

no problem, I appreciate precision.

Cheers

edit:

I just went back to the original BD files and checked 0%, 50%, 100% average stimuli were 21.60%, 21.98%, and 22.68% so there appears to be a problem in transcoding the .m2ts files to mp4.
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Old 05-31-2013, 04:35 PM
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I've been thinking about the GCD APL greyscale pattern set again today. Each of those patterns has a colour depth of 8 bits. In each the measurement window is one ninth of the area of the full pattern, as far as I can tell. The other eight ninths are the background and, ignoring the writing on each slide, I will assume the background is the same colour everywhere.

Now it turns out that it is mathematically impossible to construct an APL pattern set that way, whatever the APL you choose.
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Old 05-31-2013, 05:44 PM
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If by APL you mean constant luminance then yes, you can't do it with that geometry but that is not the intent. They are designed to be 22% constant stimulus.
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Old 05-31-2013, 10:37 PM
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Quote:
Originally Posted by zoyd View Post

If by APL you mean constant luminance then yes, you can't do it with that geometry but that is not the intent. They are designed to be 22% constant stimulus.

I didn't make it clear, but I did mean constant stimulus. I don't think a 22% constant stimulus is possible for patterns containing only two different pixel values (for window and surround) where the window area is one ninth of the total pattern area.

E.g., consider the pattern with the 100% stimulus window. For every one 100% stimulus pixel in the window area there are eight of stimulus level S in the surround. For the average stimulus of the whole pattern to be 22%, the following must hold:

(8S + 100)/9 = 22

We can solve for S with this result:

S = 98/8

So each pixel in the surround needs to have stimulus level 98/8 %. The
nearest 8-bit greyscale value is the nearest value to 255 * 98/(800) = 31.2375. That is, it is 31. But then the APL is:

(8S + 100)/9 
= (8 * (100 * 31/255) + 100)/9 
= 21.92 %

I know that's only a small error, but it does illustrate that these pattern types are problematic. And in fact you can't choose any APL value that fixes the problem.
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Old 06-01-2013, 03:45 AM
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oh yeah, well unless you want to dither to simulate higher precision that's what we are stuck with. A 30% window is really 30.317% on the GCD disk and 29.6804% on the AVHSD disk.
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Old 09-27-2013, 04:44 PM
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I've got a good adjustment on sam e450..I put up white patch around 15% size matched it to iPad but made tv less blue.then added 2-4 notches blue gain,2-3 less red gain.Added about 1 blue bias,reduced 1 red bias.(just adjusting green gain 2 notches suprisingly made Noticable difference)...Thanks to Doug B as the tip about allowing for just a bit of the abl was what helped....still experimenting here



Ps thanks to zoyd and others all the work and info for calibrating/adjusting tvs.
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Old 10-06-2013, 01:59 AM
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I know this probably sounds tacky but has anyone put up black bars around sides and lower part of screen for watching hockey or bright stuff too Improve the contrast? I would think someone running tv with computer would be able to insert black bars,but how would one do it without a computer? Preferably unexpemsive way.wink.gifeek.gif
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Old 10-06-2013, 06:00 PM
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The TV frame should already be black and the images on the screen (for hockey) will not get any brighter so there's no way to use black velvet or some other fabric to improve perceived contrast. You are talking about a display technology that will produce, say 35 fL for the hockey ice if you make the image fill only about 10% of the screen area with the rest of the screen black. If you then enlarge that image to fill the entire screen, you are only going to get about 17 or 18 fL for the white ice. You can't stop that nor can you make the contrast seem higher by some trick.

It MIGHT look brighter if you sit closer and have the image fill your field of vision more completely, but you can't get TOO close or you will start seeing the pixel structure. Projection screens look plenty bright if you can get 16 fL... that only works because the projection screen is usually quite a bit larger than a flat panel display and the screen fills a larger angle of view than a flat panel in the same space and seating distance. You can kind of simulate that with a panel display, but it involves moving closer to the panel to increase your viewing angle. There are viewing angle calculators online that you can search for. About the largest viewing angle you should attempt would be 45-50 degrees. In the viewing angle calculator, enter the width or diagonal size of your display (as required by the calculator app) and vary the seating distance until you get somewhere in that 45-50 degree angle range. If you can see too much pixel structure in the images a that distance you might have to back-off to 40 degrees but that will also make the "brightness" effect smaller.

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Old 10-11-2013, 09:07 AM
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Old 10-11-2013, 12:24 PM
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May I pretty please ask for corect patterns to calibrate st60 plasma..I've tried 10% normal windows and them seems to leave a green push. I'm almost sure that corect are APL ones but I don't know the corect size. I want to calibrate tonight so I'm looking forward for your answers. Thank you!
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Old 10-11-2013, 01:04 PM
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Quote:
Originally Posted by Andrei_VVB View Post

May I pretty please ask for corect patterns to calibrate st60 plasma..I've tried 10% normal windows and them seems to leave a green push. I'm almost sure that corect are APL ones but I don't know the corect size. I want to calibrate tonight so I'm looking forward for your answers. Thank you!

I've tried just about every size pattern on my GT30 and I have come to the conclusion that masciors 4% apl patterns gave me the best results visually.

My poor Pansonic has been a genui pig since I've gotten my Colormunki Display and since no pro can really give a definitive answer on which patterns are best, I tried them all and experimented with all types of different disc's and read hours of forum speak and dung:D.

So Andrei try the 4% apl from masciors disc then pop in the opening chase scene from Skyfall as there are alot of great scenes to judge.

If all else fails try another size pattern and watch it for a day or two to observe it.
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Old 10-11-2013, 01:20 PM
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Thank you! I tried them too! Seemed ok.., It will be so nice if a calibrator would give this secret away smile.gif I don't have any calibrators in my coutry. Bumtious on avforums uses 11% normal windows. That can't be right...
Thank you again for your answer!
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Old 10-11-2013, 01:29 PM
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what size windows does THX use? and how small is too small and how large is too large? (I'm asking about standard windows only, not APL windows)
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Old 10-11-2013, 01:39 PM
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Thx uses 6,5% if I'm not mistaken!
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Old 10-11-2013, 04:10 PM
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I would not use below 10% or above 25% normal windows on a plasma, but APL at constant luminance like Mascior's patterns are the safest bet. A 10-step 10% window drives the display through the luminance range of approximately 0.06% to 10% peak light output, so the first 4-5 patterns generate luminance levels well below where the display will normally operate. In general 15-25% patterns give you very close to the same transfer function response as do APL patterns at fixed 15% luminance (Mascior's patterns) but there is no reason not to use APL patterns to begin with.
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Old 10-11-2013, 04:30 PM
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Thank you zoyd! Would be better to use large or small apl patterns from mascior's? Gamma 2.3-2.4 or itu? Thanks again! (for what you're doing with hcfr too)
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