AWARE SYSTEMS
TIFF and LibTiff Mail List Archive

Thread

2006.12.05 15:52 "[Tiff] Grayscale, or is it?", by Joris
2006.12.05 17:18 "Re: [Tiff] Grayscale, or is it?", by Bob Friesenhahn
2006.12.05 22:56 "[Tiff] Re: Tiff Digest, Vol 31, Issue 3", by Glenn Widener
2006.12.06 20:56 "[Tiff] Re: Grayscale, or is it?", by Joris
2006.12.06 21:57 "Re: [Tiff] Grayscale, or is it?", by Graeme Gill
[...]

2006.12.06 21:57 "Re: [Tiff] Grayscale, or is it?", by Graeme Gill

I'm forever having trouble with grayscale in TIFF, except that now I really need to resolve it and make a final descision.

I see three possibilities.

[I sent this yesterday, but it seems to have gone via the
  bit bucket...]

You've left out possibility 4) - in the printing world, greyscale is the K (black) channel. It's response is whatever the printing system I'm using it on is. Note that it has the opposite sense to an additive display's response (0.0 = white, 1.0 = black).

The reality is that people abuse the image transportation mechanism (ie. TIFF, PostScript etc.) to transport their device dependent data, and don't really care whether they've labelled it accurately or not. Officially in PostScript, the device grey is meant to be an additive, "gamma = 2.2" type space, but in practice people with a printing bent simply invert their K data, and call it "grey".

The modern approach is to transport the device dependent colorspace data, and label it with an ICC profile.

Graeme Gill.