Ivan Kadomin wrote:
I'm trying to calibrate and profile my display. In it's OSD panel there are some presets "Standard", "sRGB", "AdobeRGB", etc. and also "Custom Colors".
Hmm. It seems to be missing an important setting, something that would be called "Native" !
In all modes except the "Custom Colors" Contrast and Brightness settings are available only. In "Custom Colors" in addition to RGB Gain and RGB Bias controls there are RGBCMY Hue/Saturation controls. In dispcal utility there are options that help user to properly setup RGB Gain and RGB Bias. But how should I act to setup RGBCMY Hue/Saturation controls of the display properly?
Basically the RGBCMY controls are applying an interpolation to map the incoming RGB to the native RGB. So if you are not trying to emulate some other color space in hardware (like sRGB or AdobeRGB), then you should be trying to set the RGBCMY controls to maximum gamut. Now if these controls have been done well, you won't be able to set them beyond the native gamut of the display. If they've been done badly, they will let you set values beyond the native gamut, and there will be clipping, which would be bad. One idea for figuring out what's going on would be to setup dispwin -n -m and spotread -e, and adjust each color for maximum chrominance - a^2 + b^2 (Sorry about that, I'll add an LCh display mode to spotread to make such things easier). If you get to a point where you increase the controls and nothing changes, you know it's clipping. If the controls are in xy coordinates, then you could try spotread -e -x, which will show Yxy. A shortcut would be to figure out the best (most saturated) RGB values, then compute the straight line xy values between these for the CMY values, since this will be the case for an additive device. The advice for Hue/Saturation is similar. You would need to discover what the "do nothing" or "native" settings are. [The manufacturer sure aren't making this easy!] Graeme Gill.