Author Topic: Grayscale Conversion node defaults  (Read 3310 times)

Is there any way to change the default channel contributions in the Grayscale Conversion node? It currently defaults to 0.33 per channel, while the more "accepted" numbers are more like:
R: 0.299
G: 0.587
B: 0.114

Currently I have my own subgraph in a common package which only has a grayscale conversion node with those values set, though it would be nice to be able to set these defaults for the "official" node.
Last Edit: February 19, 2013, 04:48:25 pm

well, instead of hardcoding the values, maybe try the rgb-a split node.
then you have your channels, couldnt you throw in a levels node there and afterwards merge everything back together?
then plug a greyscale conversion behind that...

i'm not too sure though, i worked long yesterday :D
how do you convert with your set values, may i ask?

also, why is what you read more accepted? I never heard about that.

No need for the rgba split, that's complete overkill :p

Basically the Grayscale Conversion node does a naive RGB-to-Luminosity conversion by averaging the RGB channels ((R+G+B) / 3). However, the human eye has different sensitivities over the range of the spectrum, so the differing values simply refer to the weighting each channel receives.

So instead of
luminosity = ((R+G+B) / 3)
you have
luminosity = (R*0.299 + G*0.587 + B*0.114)

(there are a handful of alternate weightings and calculations, but the above seems to be the more commonly used).
Last Edit: February 19, 2013, 04:48:43 pm

hey, thanks for the info.
didnt know about that until now... good to know, though!

We are thinking about a global preset system for node parameters but I can't give you any details on when this will actually be implemented.

Product Manager - Allegorithmic