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

2006.12.05 17:18 "Re: [Tiff] Grayscale, or is it?", by Bob Friesenhahn

  1. Greyscale is power(R=G=B,1/2.2). In other words, we keep the intuitive notion of greyscale based on the RGB space that itself is not very strictly defined (but we could and can assume it to mean sRGB that has a better definition), but we compensate gamme. This is consistent with the above quoted remark on gamma. It is, however, likely not very common to do this, thus resulting in an unintended interpretation of most image data out there.

For scientific/sensing applications, grayscale can mean almost anything, but for most of the world grayscale is Rec.601 Luma with gamma = 1/2.2. That is because grayscale for TVs came first and color was added later. For modern computer and HDTV displays, Rec.709 Luma is more appropriate, but it is still based on gamma = 1/2.2.

Bob Friesenhahn
bfriesen@simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/
GraphicsMagick Maintainer, http://www.GraphicsMagick.org/