2006.12.05 15:52 "[Tiff] Grayscale, or is it?", by Joris Van Damme

2006.12.05 23:26 "Re: [Tiff] Re: Tiff Digest, Vol 31, Issue 3", by Toby Thain

The standard conversion from RGB to gray, documented in the textbooks, is grey level = .33R+.5G+.17B. So a unitary conversion back to RGB is fine.

Many systems - such as PostScript - use the NTSC coefficients, see http://poynton.com/notes/colour_and_gamma/GammaFAQ.html#luminance, http://en.wikipedia.org/wiki/Luminance_(video)