Originally Posted by ndaa75
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.