Digital BW, The Print

--- In DigitalBlackandWhiteThePrint@yahoogroups.com, "John Vitollo" <jvlist@...> wrote:
>
> --- In DigitalBlackandWhiteThePrint@yahoogroups.com, "Eric Neilsen" <e.neilsen2@> 
> wrote: 
> > I asked Julianne Kost of Adobe that very question a few years ago and can't
> > find her response. I'm pretty sure it was either 70G/20R/10B or
> > 60G/30R/10B...but with my memory who knows. Guess you could manually do
> > those and see which more closely matches the RGB>Grayscale conversion.
> 
> Photoshop's default grayscale conversion is: R-30%  G-60%  B-10%
>


There are no fixed ratios.  Photoshop uses color management to convert Modes.
So if you convert RGB to Grayscale you are preserving the L values of the RGB
profile space -- converting them to identical L values in the grayscale working space.
This is easy to see: take any set of RGB patches, using the eyedropper look at the
L values, convert to grayscale and all the L values remain the same.

Conversions using desaturate, channel mixer, black&white, I think use ratios
but they are all different.

Roy