Grayscale variances - different patterns, plasma calibration

Hi all,

Bit of a noob question here. I recently have managed to get a fairly decent image on my Panasonic 55VT30b (UK) plasma using the AVSHD normal windowed patterns, however when i check with small or large APL's the greyscale at each brightness interval has deviated from the 'original' calibration performed with windows. Is this wrong? I was under the impression that the greyscale should remain the same regardless of pattern used?
To clarify, I use a specific technique for dialing in the Panasonic given its well documented issues with calibration and this was adopted on all tests to ensure the best chance of accuracy for the final result.

Thanks for your help.

Indeed.

The long of the short of it is then that a plasma display is inaccurate regardless of what process you use to calibrate.
So this therefore leads me on the the next question - this is probably been asked dozens of times but just want to be sure.
I have used both small apl, large apl and window patterns to calibrate - some people tell me to use the smallest ones available, others say the large APLS and even others say windows. As you can appreciate from a 'noob' perspsective is there a logical approach to calibrating a plasma display in order to gain the most accurate picture and if so what is the 'recommended' formula to achieve this? Do you use small windows to minimise the effect of ABL or do you use a pattern that resemles general viewing? There seems to be arguments, even amongst the pro's as to what one should use.

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?

Thanks Steve

Its apparent then that actually trying to set a flat gamma on a plasma screen is essentially a waste of time since without knowing the ins and outs of the
ABL and the way it works with a particular display means you are shooting in the dark and can potentially end up making matters worse, as per my example.

Best approach then is to calibrate greyscale and gamut only, leaving the gamma alone.I have found that certainly in the case of the UK Panasonic VT30 range that colour decoding is skewed, with an expanded gamut a result ensuring both 25 and 50 hit their targets as close as possible.

Hi Steve, other pros and enthusiasts,

Perhaps you're better positioned to explain something to me here.

Specifically in respect of Panasonic plasmas, they have a gamma option.
You can choose 2.2, 2.4, 2.6, etc etc.
Now what does this mean in real terms?
Does it mean that Panasonic have engineered their displays and implemented their gamma settings based on the sets ABL functionality?
If this is the case then that would then lead me to believe there is a specific pattern size to be used to gain a virtually linear 2.2 gamma or certain user defined gamma level, which would be the one to use for calibration.

I note that some people here and on other forums have suggested 10%-18% windows, apl's (some saying apls produce a non accurate result - how so?) in order to accurately calibrate a plasma display. Well how do they know what the right size is given how ABL impacts a calibration from the start? It's a moving target and you can really only know what pattern to use if you know how the ABL functions? Does this mean some amongst us know this info or is it a case of making a gamma graph look impressive when we post our proud calibration results in a forum such as this one?