Why does the ICE "Color to Brightness" node have weird weight values? (0.3, 0.59, 0.11)

[Alan Fregtman]

Hey guys,

I always wonder why the "Color to Brightness" ICE node comes with the
default RGB weight values of 0.3, 0.59 and 0.11.

Is there any reason it's not 1,1,1? Who came up with these seemingly
arbitrary numbers and why are they so?

Cheers,

-- Alan

[Ben Houston]

Perceived luminance, see the first answer here:

http://stackoverflow.com/questions/596216/formula-to-determine-brightness-of-rgb-color

-ben

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Ben Houston
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Exocortex - Passionate CG Software Professionals.

[Alokgandhi]

These are settings for 'perceived luminance'. Human eye is most sensitive to green color, then to red and least to blue. What that means is that for a given RGB value, the brightness or luminance is calculated as: 0.3 x R + 0.59 x G + 0.11 x B.

Thereby we assign weights to the various color components based on human eye model. You can easily see that 0.3 + 0.59 + 0.11 = 1. So for any given color space like 0 - 255, for any given RGB value, the brightness will be from 0 - 255 as well.

These numbers are not at all arbitrary as might appear. In fact the this model was used for Television as well. There are other few formulae as well having different breakup of components. But I guess this is the most preferred one.

Sent from my iPad