Colors (OT)

[lisztfr9]

Apologize for the OT, it's about RGB and yellow.

I had to make some colors correction on a monitor, figuring out that to remove the yellow tint i had to decrease the brightness of green, then add some blue to compensate. Because green is a blend of yellow and blue. So far...

But how to obtain a yellow square ? i should display green, since there are green tiny TFT units in the LCD panel, but i can't remove the blue from this green, right ? the blue pixels can't display negative blue light, can't remove blue from the green pixels...

So obviously i'm missing something... with red, green, and blue pixels, obtaining yellow requires to display green but then, there is no way to subtract blue.

ok i'm stupid. :confused:

[LemMotlow]

Because green is a blend of yellow and blue. No it isn't. RGB is an additive system, not the same color mix system used in printing. In RGB, green isn't a blend -- it's a primary color.:

primary colors:
--------------
Red
Green
Blue

secondary colors:
----------------
Red + green = yellow
Green + blue = cyan
blue + red = magenta

If something looks too yellow, either reduce red and green (yellow), or add blue.

If you're trying to calibrate a consumer PC monitor or TV by eyeball alone, you're in for an extremely difficult time. If as you say your monitor doesn't have separate controls for each color Red, Green, and Blue, you're fighting a losing battle anyway. Are you working on a TV or PC monitor with just a "Tint" control for color? It won't work for many color balance problems.

[feisty2]

For most ycbcr videos
All 3 planes are a blend of rgb channels
But
Y = g (roughly)
U = cb = b (roughly)
V = cr = r (roughly)
Maybe something like this on plane u would help
Mt_lut ("x 128 - 0 > x 1.24 * x ?", y=2, u=3, v=2)