Timo and linear coding

The issue of linear and nonlinear coding has received a fair bit of discussion among the Usenet newsgroups lately, as a result of a dust-up between me and Timo Autiokari. Timo contradicts the most basic principle of the Gamma FAQ. He claims linear intensity coding must be used, even with 8 bits per RGB component (or perhaps especially in 8 bits).

The skirmish started on 1998-02-25, when Timo published an open letter in a Usenet posting, some inflammatory remarks concerning my Gamma FAQ. Some of those postings contain serious misunderstandings about image coding, and even a few personal attacks. These remarks are sufficiently grave that I felt obliged to respond. You can read about the Timo incident, and you can read about Timo's technical argument.

I have prepared a series of notes that comprise an introduction to Linear and nonlinear coding. At the bottom of several of these notes, you will find a link to the version of that issue as described by Timo. If you're a stoic, read just the Timo thread among those notes:

Nonlinear coding is accommodated - or required - in PhotoCD, PNG, JPEG, JFIF, sRGB, PhotoFlash, and all of the major high-quality file formats of all the major digital photography vendors. Timo claims that I have mislead the leading scientists at the "major players." By this, I think he refers to the proponents of the file formats that I mention: Kodak, Hewlett-Packard, Microsoft, Adobe, Silicon Graphics, C-Cube, and others.

See also: Concerning Timo - Timo's technical argument - Linear and nonlinear coding - Gamma FAQ

Charles Poynton
Copyright © 1998-03-12