Graeme Gill skrev 2012-02-12 23:11:
Well, the reason I was a bit unimpressed is because this is supposed to be one of the very best TV sets to buy, and it includes full ISF controls for managing grayscale at 10% stimulus steps. Color however is only at 100% stimulus. So I can nail in the grayscale and gamma to mostly perfect result (according to the patterns used, i.e full windows cause lightness to drop a bit). Color however seems a bit more difficult. Now it is possible I have used the CP software wrongly at the 75% color intensity. It has a 75% Rec. 709 setting that I assumed should be used for the 75% W+ 75% RGB measurements. But maybe I should measure all those at 100% Rec. 709 setting since i assume the Rec 709 standard is linear? When using 75% patterns all that happens is that luminocity falls a bit, but it is all realite to white which is measured as a baseline... ?Kristian Jörg wrote:When I calibrate my Panasonic VT30 plasma (not connected to a PC) with an external program i.e ChromaPure I get dE errors in the range of 1.0 or less. The color calibration is done at 100% stimulus. But when I check the color balance at 75% stimulus I get errors of about 10 dE! Ouch! There is no way of correcting that in the TV set's controls even though it has a very thorough CMS module.It depends so much on what sort of controls the TV has. TV and computer systems are really at the opposite end of the spectrum when it comes to how color is expected to be handled. The lowest common denominator for computer systems is pretty simple hardware color control (the video card per channel lookup tables), and sophisticated software driven color profiling and CMM (ICC profiles). TV sets seem to assume that color management can only be done in hardware, and so you are at the mercy of whatever random hardware and controls they provide (but may not document or provide tools for). Mostly it seems pretty dismal (an extension of the user "brightness" and "contrast" knobs. "RGBCMY" primary controls that don't work so well, etc.) Maybe some per channel curves that aren't really publicly documented, or that you'd have to write software to access. They do meet in the middle somewhere at the high (but rather proprietary) end - some displays have 3D cLUT in hardware capability (things like digital cinema displays have this capability, as well as some high end monitors), so ICC profiling type approaches can be used to create a device link cLUT to provide an emulation transform. Computer systems are capable of implementing 3D cLUT devce links at speed using the GPU. So I'm not at all surprised to hear such problems with TV calibration :-) The TVs may simply not have the capability of doing anything other than very simply calibration.
The question is when profiling a PC display with Argyll (or similar profiling software), does it correct color at different levels of stimulus or only at 100%? I.e if I would us my TV set as a PC monitor would the profile correct the color balance from 0-100% stimulus?Argyll can be used to setup an accurate emulation (within the capabilities of the device) of any colorspace. For displays, a combination of hardware calibration and ICC profling& linking is the means of doing this, but the normal means of using the full color transforms involves running the color through a 3D cLUT. Typically that's done in software, although a GPU can do this in real time. While the mechanisms for applying ICC profiles in software are fairly clear, the current means of doing similar things with video are far from clear.
I will not use Argyll to profile the plasma. I do use the plasma as hocked up to a HTPC. But since that same plasma calibration should be used for a standalone bluray and other equipment it becomes more of a special case then. Better calibrate the display only to accomodate all equipment equally.
I will however calibrate/profile my standard workstation real soon now :)