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Grayscale variances - different patterns, plasma calibration - Page 3

post #61 of 273
11/28/12 at 8:42am
Quote:
Originally Posted by fallengt View Post

Is that true? So.. to calibrate Plasma, we have to use APL windows patterns and set color gamut higher than (D65) target for the screen to be look good in real content? but how much wider(exactly..) w/o over-saturated color ?
The out of the box True Cinema of my Panasonic St50 has gamut very close to D65 reference but somehow I feel like it's undersaturated when watching HD movies, ABL probally is the answer.
What ? is that true ? eek.gif
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post #62 of 273
11/28/12 at 8:42am
Quote:
Originally Posted by jdoostil View Post

ETOF is the new expression for gamma

it's not a new expression
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post #63 of 273
11/28/12 at 8:50am
Quote:
Originally Posted by mlg33 View Post

What ? is that true ? eek.gif
no wink.gif
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post #64 of 273
11/28/12 at 9:04am
Quote:
Originally Posted by realzven View Post

no wink.gif
I just quote him or...he didn't mean it that way?

Quote:
With plasmas is it mainly bright scenes that are contrast reduced, which also alters gamut (saturation).
To get a plasma to 'look' good (ie, look accurate) you often have to set gamut wider than the desired target when calibrating.
This is a trick we have used a number of times, when the actual calibration data states it is correct, but the visual results look poor.
Unfortunately, ABL is anything but linear...
And, it reacts differently to different colour ratios, due to the fact different colours have different underlying luma values for what 'appear' to be similar brightness colours...

Quote:
Originally Posted by realzven View Post

and the greyscale of the ST50 OOTB is good ?
Red/green track very good but color temp is a bit cool (~6800-7000K)... work as intended I suppose
Edited by fallengt - 11/28/12 at 9:15am
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post #65 of 273
11/28/12 at 9:18am
Thread Starter 
OK, tried the GCD large APL windows - didnt touch the VT30's 10 pt gamma at all - the result inlcuding calibrating the CMS at 75/75 is certainly the best ive seen so far on this set - although the gamma when charted was far from linear, especially at 80/90 with any adjustment in the 10pt to iron it out just introduces posterization. Guess thats the ABL. MLL was impressive though using the GCD disk, had a reading at 0.0033 fl using a profiled i1Dpro.
The only thing im not liking about this set is the brightness limitation - a nightmare - considering swapping this out for a 60E6500 Samsung plasma-if the picture was brighter it'd be a winner hands down.
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post #66 of 273
11/28/12 at 10:33am
Quote:
Originally Posted by turbe View Post

it's not a new expression

new for him smile.gif
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post #67 of 273
11/28/12 at 11:53am
Thank you all. I had heard and read about it before, just not the abbreviated version. Gamma in conjuction with ABL is the hardest thing to grasp at the moment.
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post #68 of 273
11/28/12 at 12:46pm
Thread Starter 
Quote:
Originally Posted by zoyd View Post

The optimal gamma calibration for plasma technology will be obtained using fixed average APL stimuli in the 20-40% range (see gory details/measurements here). The GCD disk contains such a pattern sequence for grayscale, gamma and CMS work at 22% fixed APL with 10% windows. These patterns will optimize your plasma calibration over the majority of material you will ever view (excluding hockey).

Whilst the GCD patterns give me a pretty good grayscale, using them to set a linear gamma on the Panasonic VT30 range doesn't work at all. Infact the only pattern that gets me close to a linear gamma are small APL's - I think Panasonic have engineered a liar.
Perfect graphs on Calman give a skewed image which makes me question the results the pros obtain with the VT30 sets given their graphs are immaculate. How come? Now I know the euro panasonic Vt30 range are slightly different than the NA versions however the sets show virtually identical behaviour in almost all aspects of calibration.

Strange.
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post #69 of 273
11/28/12 at 2:51pm
Quote:
Originally Posted by ndaa75 View Post

Whilst the GCD patterns give me a pretty good grayscale, using them to set a linear gamma on the Panasonic VT30 range doesn't work at all.

What do you mean by "doesn't work"? You can't get it linear with the 10pt control or you can get it linear but it generates some other problem when viewing reference material?
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post #70 of 273
11/28/12 at 11:26pm
Thread Starter 
Quote:
Originally Posted by zoyd View Post

What do you mean by "doesn't work"? You can't get it linear with the 10pt control or you can get it linear but it generates some other problem when viewing reference material?

Oh yes I can get it linear, but doing so using the individual gamma sliders in the 10pt system introduces some unwelcome effects especially where larger individual adjustments are made.
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post #71 of 273
11/29/12 at 2:24am
Quote:
Originally Posted by Chad B View Post

Have you tried calibrating to the small APL patterns on AVS 709? I know in the 1st post you said you checked them and they gave a different result, but I think using them would be worth a try. I have not tried them on a VT30, but I have tried them on other plasmas with good results. Others have said that they have gotten good results with the large APL windows from the same disc.

Chad,when you calibrated using small APL patterns on avs709 did you use the same small patterns to set your color gamut as well,or do you use the standard windows for color?
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post #72 of 273
11/29/12 at 4:18am
Quote:
Originally Posted by PeterLewis View Post

Chad,when you calibrated using small APL patterns on avs709 did you use the same small patterns to set your color gamut as well,or do you use the standard windows for color?
Same.
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post #73 of 273
11/29/12 at 4:36am
Quote:
Originally Posted by Chad B View Post

Same.

O.K Thanks buddy...
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post #74 of 273
11/29/12 at 7:11am
Thread Starter 
At the risk of going off at a tangent here, thought i do a few comparisons with various patterns.

I used the GCD disk to calibrate my grayscale virtually perfectly at all points - using the 1% APL patterns.
I then took readings at other stimulus points with other patterns and recorded the data as R,G and B percentages.
I found that the two patterns that were actually more or less the same in terms of producing similar output were the AVS window patterns and the AVS small APL, both gave virtually the same reading at 40%, 50% and 80% whereas all the remaining patterns were a little way off (>1% on each RGB channel). However the Small APL isnt impacted by the ABL of the Panasonic as much as the window pattern, so I intend to use the latter as my preferred pattern for this display. Still having issued with the gamma though, so perhaps will just leave it as it is the picture is still stunning.
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post #75 of 273
11/30/12 at 9:12am
Forgive my English ndaa75, but you chose the window pattern to calibrate the Panasonic plasma ?

Thanks
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post #76 of 273
11/30/12 at 11:03am
Thread Starter 
Mlg33, yes I did - going to have a go with the small APL as well to see what result that gives.
Also wondering whether the pros are able to share how they managed to achieve a linear gamma without any visual issues on a low brightness setting which is what the Uk models are stuck in - pretty stupid setting to lock in to be honest - how they ever thought it was a good idea is beyond me.
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post #77 of 273
11/30/12 at 2:21pm
ndaa75

I don't think it had anything to do with it being a good idea or not. It had to do with energy consumption and what they had to do to reduce in order to sell this display in their market.
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post #78 of 273
11/30/12 at 2:33pm
That would make sense if all presets were capped, but on my VT50 the THX brightroom could function as a lighthouse (52+ftl) and the isf preset is far too dim for a plasma (23ftl).
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post #79 of 273
11/30/12 at 2:35pm
Thread Starter 
Quote:
Originally Posted by JimP View Post

ndaa75
I don't think it had anything to do with it being a good idea or not. It had to do with energy consumption and what they had to do to reduce in order to sell this display in their market.

Sorry but that's nonsense. All other modes on this set are considerably brighter - poor decision making by management in my opinion that's left them in the wake of their competition. You'll note the NA version suffers no such issue.
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post #80 of 273
11/30/12 at 3:47pm
The reason it was capped was to conform to studio level peak white of 80 cd/m^2. Why they did this in the European market I don't know.
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post #81 of 273
11/30/12 at 4:43pm
Thread Starter 
Quote:
Originally Posted by zoyd View Post

The reason it was capped was to conform to studio level peak white of 80 cd/m^2. Why they did this in the European market I don't know.

Silly move considering a vast majority of people do not live in a studio - would have been an easier move to not cap the brightness and let the user decide.
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post #82 of 273
11/30/12 at 4:52pm
According to David Mackenzie (hdtvtest), this has been typical of the vt line pro modes in that market. The non-pro modes and the st are not capped.
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post #83 of 273
12/1/12 at 12:41am
Thread Starter 
Quote:
Originally Posted by zoyd View Post

According to David Mackenzie (hdtvtest), this has been typical of the vt line pro modes in that market. The non-pro modes and the st are not capped.

Indeed. Picture is amazing though at about 4pm onwards on a winters day!
Need some help setting gamma on this thing, have you had any experience with these sets zoyd?
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post #84 of 273
12/1/12 at 4:09am
no, DNICE mentioned at the shoot-out that the 10 pt correction does not work right with the main problem being that points in-between the corrected levels were not interpolated linearly. There might be some tricks for that as well as the banding you mentioned but I've never worked on one. First thing I would try would be tweaking sub-contrast in the service menu if it's available. That might allow you to shift the contrast scale across the 10 pt control points to better smooth it out. If you're lucky you could increase peak white there as well.
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post #85 of 273
12/1/12 at 4:32am
zoyd

Was that 10 pt comment by dnice more to do with grayscale or gamma?
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post #86 of 273
12/1/12 at 4:58am
The comment was in reference to grayscale, he pointed out chromaticity shifts of several dE at some of the 5% levels. But since the white point is determined by each individual color EOTF I would expect that this also creates wiggles in gamma at those points.
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post #87 of 273
12/1/12 at 5:14am
Quote:
The reason it was capped was to conform to studio level peak white of 80 cd/m^2. Why they did this in the European market I don't know.

That is rather stupid, as virtually all 'studios' in Europe work to the international standard of 120 Nits...

The EBU spec is actually "70 to at least 100 cd/m2"

But, also states "100% luminance on the screen is defined as the luminance of a luma signal of digital level 940, but levels 941 through 1019 should also be correctly displayed and should track any adjustment made to the 100% luminance level."

Which for most operation means 100% white (1019, or super white) at about 120 Nits.

mad.gif
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post #88 of 273
12/1/12 at 12:36pm
Quote:
Originally Posted by ndaa75 View Post

You see the problem I have with my Panasonic VT series is that I am unable to achieve a flat gamma without consequences ie a bad case of contouring and posterization. This seems apparent on all pattern types and especially where larger adjustments are made to a single gamma channel in order to flatten the line out. Perhaps this is the result of an aggressive ABL function - anyone have a work around?

The contouring and posterization is a result of the digital processing path not having enough "headroom". More than likely, video processing in that display is done in a 10-bit data path... that's simply not enough "space" to make many changes without getting into clipping... and it's the clipping that results in posterization/contouring when there was none previously.

That said, there's nothing wrong with 10-bit processing of 8-bit video data... Lumagen Radiance video processors have a 10-bit data path and never exhibit problems with contouring or posterization. But it is easier to get into contouring and posterization when a consumer product is limited to 10-bit processing. Samsung displays have had 18-bit data paths for at least the last 4 years, possibly longer. They have extensive and comprehensive calibration controls compared to most TVs and all the controls can be used over their entire adjustment range without ever producing artifacts (contouring or posterization). The WORST case I've ever seen is Toshiba displays that have color calibration controls... some models had a range of +/- 30 but any adjustment over +/- 10 would produce TERRIBLE posterization... more recent Toshiba models could only be adjusted within a +/- 3 range though the control range was smaller also.

So... what this means is... you may be able to use some of the controls for calibration, but you might have to limit how much adjustment you use in order to avoid contouring or posterization from plaguing the calibrated images. This is one case where better measurements should probably be sacrificed in the name of fewer visible artifacts.

Lumagen with their 10-bit processing path recommends that you calibrate-out (at least) the worst errors in the TV or projector using the TV's or projector's controls, and fix the remaining things with the Radiance processor's controls. That avoids making big moves in either product because it is the big changes where you can run into headroom issues and bit-allocation issues that result in visible contouring/posterization.

Having an 18-bit data path isn't an automatic fix for contouring/posterization problems. It could STILL be screwed up if the 18-bit data wasn't converted back to 8-bits appropriately.
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post #89 of 273
12/1/12 at 2:01pm
The problem with most plasmas is the displays on most are a lot less than 8 bits - actually around 5 to 6 bits.

This means that with almost any internal change that are more than simple setting changes (pre-set gamma, etc) it is very likely there will be banding issues.

frown.gif

10 bit processing will rarely show banding on an 8 bit display - even with major changes.

Steve
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post #90 of 273
12/1/12 at 2:11pm
Thread Starter 
Quote:
Originally Posted by Doug Blackburn View Post

The contouring and posterization is a result of the digital processing path not having enough "headroom". More than likely, video processing in that display is done in a 10-bit data path... that's simply not enough "space" to make many changes without getting into clipping... and it's the clipping that results in posterization/contouring when there was none previously.
That said, there's nothing wrong with 10-bit processing of 8-bit video data... Lumagen Radiance video processors have a 10-bit data path and never exhibit problems with contouring or posterization. But it is easier to get into contouring and posterization when a consumer product is limited to 10-bit processing. Samsung displays have had 18-bit data paths for at least the last 4 years, possibly longer. They have extensive and comprehensive calibration controls compared to most TVs and all the controls can be used over their entire adjustment range without ever producing artifacts (contouring or posterization). The WORST case I've ever seen is Toshiba displays that have color calibration controls... some models had a range of +/- 30 but any adjustment over +/- 10 would produce TERRIBLE posterization... more recent Toshiba models could only be adjusted within a +/- 3 range though the control range was smaller also.
So... what this means is... you may be able to use some of the controls for calibration, but you might have to limit how much adjustment you use in order to avoid contouring or posterization from plaguing the calibrated images. This is one case where better measurements should probably be sacrificed in the name of fewer visible artifacts.
Lumagen with their 10-bit processing path recommends that you calibrate-out (at least) the worst errors in the TV or projector using the TV's or projector's controls, and fix the remaining things with the Radiance processor's controls. That avoids making big moves in either product because it is the big changes where you can run into headroom issues and bit-allocation issues that result in visible contouring/posterization.
Having an 18-bit data path isn't an automatic fix for contouring/posterization problems. It could STILL be screwed up if the 18-bit data wasn't converted back to 8-bits appropriately.

Thanks for the explanation Doug.
My Samsung D8000 plasma by comparison was an absolute dream to calibrate - fully done within an hour! By comparison the Panasonic is a pig. Gonna try and swap it out.
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