Plasma Calibration - understanding ABL / Correct patterns to use - AVS Forum
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post #1 of 4 Old 11-12-2012, 05:18 AM - Thread Starter
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Hi All

Having some issues trying to calibrate my Panasonic 55VT30 plasma, dont seem to ge the right colouration in light areas when calibration has been completed - been using the 10% APL patterns on the GCD disk. Anyways i decided to take some measures from both the AVSHD and the GCD for all pattern types to compare the different values. Am I right in assuming that my plasma has quite an aggressive ABL from the attached graph with all patterns except the 1% apl and small apl pattern? If so does this indicate that I should use either of these two patterns in order to gain an accurate calibration?

Appreciate your help.

Various Pattern Measurements AVSHD and GCD Panasonic TXP55VT30.pdf 27k .pdf file
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File Type: pdf Various Pattern Measurements AVSHD and GCD Panasonic TXP55VT30.pdf (27.2 KB, 58 views)

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post #2 of 4 Old 11-13-2012, 11:34 AM
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The problem with plasmas is you actually need to match the patch size to the impact ABL has on that particular display.

The problem is that when ABL kicks in it is in a different point based on the scene brightness/contrast for different displays.

So, if the patch size is too small you will calibrate for a different level of ABL interaction compared to real images.
But, then, there are no guarantees on the real images you will be looking at...
And that means there are no real answers to the correct patch size.

The best will be to profile the display and measure the ABL effect on different patch sizes and chose the best compromise for that particular display.

Rule of thumb - the more aggressive the ABL the larger patch size you actually need - up to a point.
And yes, that is counter intuitive to what you might expect....

Steve

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post #3 of 4 Old 11-14-2012, 01:23 AM - Thread Starter
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Quote:
Originally Posted by Light Illusion View Post

The problem with plasmas is you actually need to match the patch size to the impact ABL has on that particular display.
The problem is that when ABL kicks in it is in a different point based on the scene brightness/contrast for different displays.
So, if the patch size is too small you will calibrate for a different level of ABL interaction compared to real images.
But, then, there are no guarantees on the real images you will be looking at...
And that means there are no real answers to the correct patch size.
The best will be to profile the display and measure the ABL effect on different patch sizes and chose the best compromise for that particular display.
Rule of thumb - the more aggressive the ABL the larger patch size you actually need - up to a point.
And yes, that is counter intuitive to what you might expect....
Steve

Thanks Steve

Therefore judging from the graph i attached the AVS HD windows or Large APL windows would indicate they would be more favourable for my display?
I tried the 10% APL in the GCD disk and found that whites had a magenta / green 'ringing' to them, like light relfections of peoples heads for example - when I used the small APL sizes they are are lot less obvious.
As a novice I still require guidance and having an underrstanding of the what im actually doing is key to arriving at a logicial conclusion in respect of a workable process, so appreciate your time and your response.

Many thanks again Steve.

Benq W1080ST Projector, Panasonic TXP55VT30 plasma, Yamaha RXA3020 AVR, Denon DVD-2500BT, Q Acoustics 1010i in 7.1, i1 Pro spectro, i1 Display Pro, Calman 5 Enthusiast, PS3, Xbox 360, Wii

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post #4 of 4 Old 11-14-2012, 03:57 AM
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Quote:
I tried the 10% APL in the GCD disk and found that whites had a magenta / green 'ringing' to them, like light relfections of

Highlight colours like that tend to suggest early clipping in one or other of the colour channels.
Test with the ContrastCal image from the Callmages downlaod from the Light Illusion website.
(follow the 'Initial Display Calibration' page instructions.)

Steve

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