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post #1 of 24 Old 09-07-2013, 09:46 AM - Thread Starter
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I noticed some oddness in gradients in my calibration (Panasonic VT50 plasma).

I looked at a gray ramp and saw that every place I made a "correction" in the 10 point gamma was visibly erroneous in the direction I had made it. I watched the ramp while I set all the 10 point positions to zero and it smoothed right out.

So apparently even though I can get a report in my calibration app to show very accurate gray scales, xyY, it doesn't really work.

With all set to zero it's still actually within a deltaE, so maybe it doesn't matter, but does anyone know what's up with this - or can point me to a previous discussion on it? Is it like the one exact level you're measuring doesn't necessarily reflect what's in the whole 10 IRE range? Is there a trick to adjust the 10 point gamma without this problem?
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post #2 of 24 Old 09-07-2013, 09:52 AM
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There's evidence to suggest that the 10pt adjustments on Panasonics are somewhat broken. Specifically, the controls aren't "centered" where one would reasonably expect them to be centered. This topic has come up several times ... seek and ye shall find.
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post #3 of 24 Old 09-07-2013, 10:21 AM
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Despite the issues with the controls, a perfect looking gray ramp can be achieved with the 10 point adjustments.

Hints:
Keeping contrast high and using APL windows helps.
Use PB mid.
Do 2 point white balance first, and give extra emphasis to 10% and 100% while keeping the in between levels as good as possible. As you indicated, you can get all the dE levels below 2 or so just by doing the 2 pt., but you can refine things further by proceeding.
Recheck brightness.
Do not make the adjustment in real time. Take a 10 step reading run, look at an absolute RGB tracking graph, and apply corrections to the 10 point control as indicated. For instance, if 80% shows r at -3, g at -1, and b at -2, raise gamma by 1, then raise r by 2 and b by 1. If using CalMAN 5, you will have to make larger corrections (up to a factor of 6 times at 10%) for similar appearing errors at the low end than at the high end. You will have to take multiple runs.
Do CMS.
Go back and touch up 10 point after doing CMS.
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post #4 of 24 Old 09-07-2013, 10:35 AM - Thread Starter
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Quote:
Originally Posted by Chad B View Post

Despite the issues with the controls, a perfect looking gray ramp can be achieved with the 10 point adjustments.

Hints:
Keeping contrast high and using APL windows helps.
Use PB mid.
Do 2 point white balance first, and give extra emphasis to 10% and 100% while keeping the in between levels as good as possible. As you indicated, you can get all the dE levels below 2 or so just by doing the 2 pt., but you can refine things further by proceeding.
Recheck brightness.
Do not make the adjustment in real time. Take a 10 step reading run, look at an absolute RGB tracking graph, and apply corrections to the 10 point control as indicated. For instance, if 80% shows r at -3, g at -1, and b at -2, raise gamma by 1, then raise r by 2 and b by 1. If using CalMAN 5, you will have to make larger corrections (up to a factor of 6 times at 10%) for similar appearing errors at the low end than at the high end. You will have to take multiple runs.
Do CMS.
Go back and touch up 10 point after doing CMS.

Ok, I'll try that - thank you.

It seemed to me that the changes only affected the higher levels so that adjusting in order from dark to light was sufficient. The changes finally affect 100% which makes them all wrong - so I was just setting that back to where it was.

But - obviously my technique doesn't work, so I'm hoping this will...
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post #5 of 24 Old 09-07-2013, 10:37 AM - Thread Starter
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BTW - I didn't detect any issues with the 10 point WB which I kept. I only saw errors from the 10 point gamma adjustments.
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post #6 of 24 Old 09-08-2013, 09:15 AM - Thread Starter
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Tried it - worked. Thanks again.

I deviated a little. I was so paranoid about making aggressive changes that I repeatedly did an entire read and bumped the levels by only +/- 1. It was tedious, but I was able to get the 10 point gamma and WB almost perfect - and there is no weirdness in the ramp (or visible in gradients while viewing).
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post #7 of 24 Old 09-08-2013, 10:15 AM
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Quote:
Originally Posted by Chad B View Post

If using CalMAN 5, you will have to make larger corrections (up to a factor of 6 times at 10%) for similar appearing errors at the low end than at the high end.

Just for clarity: I assume you mean this wrt using the Calman serial interface to control the VT50 directly?
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post #8 of 24 Old 09-08-2013, 10:26 AM
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I'm talking about a weighting difference in CalMAN 5 as opposed to CalMAN 4 and ChromaPure. The weighting difference makes the RGB tracking graphs on CM5 respond differently at the low end. Not differently as far as direction of error, but in amount of error. CM5 was weighted for perceptual error, whereas other software and older versions of CM are weighted for numerical error.
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post #9 of 24 Old 09-08-2013, 01:34 PM
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Quote:
Originally Posted by Chad B View Post

I'm talking about a weighting difference in CalMAN 5 as opposed to CalMAN 4 and ChromaPure. The weighting difference makes the RGB tracking graphs on CM5 respond differently at the low end. Not differently as far as direction of error, but in amount of error. CM5 was weighted for perceptual error, whereas other software and older versions of CM are weighted for numerical error.

if you choose dEUV instead of dE2000 does that make CM5 respond like CM4 and CP? or are you referring to something else than dE calculations?
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post #10 of 24 Old 09-08-2013, 01:48 PM
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Quote:
Originally Posted by PlasmaPZ80U View Post

Quote:
Originally Posted by Chad B View Post

I'm talking about a weighting difference in CalMAN 5 as opposed to CalMAN 4 and ChromaPure. The weighting difference makes the RGB tracking graphs on CM5 respond differently at the low end. Not differently as far as direction of error, but in amount of error. CM5 was weighted for perceptual error, whereas other software and older versions of CM are weighted for numerical error.

if you choose dEUV instead of dE2000 does that make CM5 respond like CM4 and CP? or are you referring to something else than dE calculations?

No, the whole CalMAN 5 dE Engine is based to that...

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post #11 of 24 Old 09-08-2013, 08:13 PM
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Quote:
Originally Posted by Chad B View Post

I'm talking about a weighting difference in CalMAN 5 as opposed to CalMAN 4 and ChromaPure. The weighting difference makes the RGB tracking graphs on CM5 respond differently at the low end. Not differently as far as direction of error, but in amount of error. CM5 was weighted for perceptual error, whereas other software and older versions of CM are weighted for numerical error.
Since dE IS a measure of perceptual error, I really don't know what this means. Could you elaborate?

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post #12 of 24 Old 09-08-2013, 10:12 PM
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Quote:
Originally Posted by Chad B View Post

I'm talking about a weighting difference in CalMAN 5 as opposed to CalMAN 4 and ChromaPure. The weighting difference makes the RGB tracking graphs on CM5 respond differently at the low end. Not differently as far as direction of error, but in amount of error. CM5 was weighted for perceptual error, whereas other software and older versions of CM are weighted for numerical error.

Got it. Thanks. ... I think ... so it's kind of like weighting the dE using the target luma(s) in the calculation as opposed to just the chromaticity? (The lower the target luma, the less "obvious" the chromaticity errors will "appear?")

PS: Sorry ... I'm probably mangling terminology again. wink.gif
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post #13 of 24 Old 09-08-2013, 11:38 PM
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Quote:
Originally Posted by TomHuffman View Post

Quote:
Originally Posted by Chad B View Post

I'm talking about a weighting difference in CalMAN 5 as opposed to CalMAN 4 and ChromaPure. The weighting difference makes the RGB tracking graphs on CM5 respond differently at the low end. Not differently as far as direction of error, but in amount of error. CM5 was weighted for perceptual error, whereas other software and older versions of CM are weighted for numerical error.
Since dE IS a measure of perceptual error, I really don't know what this means. Could you elaborate?

Hi Tom, check these graphs.

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post #14 of 24 Old 09-09-2013, 12:09 AM
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There are two ways to calculate dE for the grayscale (forgetting the differences in the formulas). Either you treat gamma separately from chromaticity errors or you include departures from your target gamma as part of the dE error. For example, say you have a target gamma of 2.22 and you have an error of excess red at both 10% and 90% stimulus of x0.317, y0.329. Let's also assume that the measured gamma at both points is too low at 2.02.

If you include departures from your target gamma as part of the dE error, then the CIE94 value at 10% is 3.2, but at 90% it is 1.9, even though the chromaticity errors are the same. This reflects the fact that human vision is more sensitive to luminance errors at low levels of stimulus. If you treat gamma and dE separately, then the CIE94 value at both levels is just 1.9.

As a practical matter, there is very little difference here. I suppose would could argue that there is some value in seeing the effect of gamma and chromaticity errors in a single number, rather than going back and forth between chromaticity errors expressed in dE and luminance errors expressed in deviance from a target gamma. It is also worth emphasizing that luminance errors at the low end are most important. On the other hand, most of us are more accustomed to treating them separately and it is useful to be able to quantify errors in luminance and chromaticity independently using gamma and dE respectively.

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post #15 of 24 Old 09-09-2013, 12:13 AM
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Quote:
Originally Posted by ConnecTEDDD View Post

Hi Tom, check these graphs.
See my post above. I can't see the graphs without a login. This is not a difference in dE calculation. It is a difference in how you define the values you are comparing--whether those values include luminance and an assumed target gamma or whether the values treat chromaticity only and leave luminance errors for an independent gamma number.

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post #16 of 24 Old 09-09-2013, 12:25 AM
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Quote:
Originally Posted by TomHuffman View Post

Quote:
Originally Posted by ConnecTEDDD View Post

Hi Tom, check these graphs.
See my post above. I can't see the graphs without a login.





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post #17 of 24 Old 09-09-2013, 01:11 AM
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Quote:
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I can't make much sense of this without the xyY values and target gamma.

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post #18 of 24 Old 09-09-2013, 08:00 AM
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We don't do anything at all to the standard dE formulas.

All of them are exactly the same as they have always been.

We do use the dE formulas to model the perceptual error for RGB balance. That way RGB balance at the low end is meaningful. If you use a percentage of total light without weighting, you get reports of large differences for colors that are almost identical. So with the method we introduced in CalMAN 5 it makes it easier for a user to know when they've got a good result.

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post #19 of 24 Old 09-09-2013, 09:45 AM
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does the "include luminance error" let you toggle between grayscale color (xy) and grayscale (xyY)?

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post #20 of 24 Old 09-09-2013, 10:02 AM
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Quote:
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does the "include luminance error" let you toggle between grayscale color (xy) and grayscale (xyY)?



For the deltaE formulas it does exactly that.

The RGB balance values are a fixed formula with no options. If you want to view RGB balance without regard to luminance our RGB relative does just that. We continue to use our relative weighting because that is more consistent with what you actually see.

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post #21 of 24 Old 09-10-2013, 02:36 AM
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After a while since the 60 series are out, is there a conclusion on what's the best method to calibrate these sets regarding patterns, technique, gama targeting (linear vs itu) etc?
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post #22 of 24 Old 09-10-2013, 02:41 AM
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I always use and view absolute and relative together on separate charts because I believe looking at one alone can lead to poor results.

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post #23 of 24 Old 09-10-2013, 11:51 AM
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Thank you! That's how I do it myself but I'm sure some calibrators here have the answer to my question if they're kind enough, since they had calibrated more panels and know how these things behaves.
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post #24 of 24 Old 09-17-2013, 04:26 AM
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Quote:
Originally Posted by Chad B View Post

Despite the issues with the controls, a perfect looking gray ramp can be achieved with the 10 point adjustments.

Hints:
Keeping contrast high and using APL windows helps.
Use PB mid.
Do 2 point white balance first, and give extra emphasis to 10% and 100% while keeping the in between levels as good as possible. As you indicated, you can get all the dE levels below 2 or so just by doing the 2 pt., but you can refine things further by proceeding.
Recheck brightness.
Do not make the adjustment in real time. Take a 10 step reading run, look at an absolute RGB tracking graph, and apply corrections to the 10 point control as indicated. For instance, if 80% shows r at -3, g at -1, and b at -2, raise gamma by 1, then raise r by 2 and b by 1. If using CalMAN 5, you will have to make larger corrections (up to a factor of 6 times at 10%) for similar appearing errors at the low end than at the high end. You will have to take multiple runs.
Do CMS.
Go back and touch up 10 point after doing CMS.

Does this display have the same problem that the VT50s have where if you do a 20/80 or 30/80 2 point balance, you wind up with lower end (below 20) red in grayscale that's not correctable using a 10pt grayscale correction?

Totally unrelated, have you compared your jeti to a i1pro2 using a Panasonic plasma and if so, what were the differences?

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