Timo -
Intensity in, intensity out

Timo desires to code everything as intensity, represented more or less accurately.

Timo considers nonlinearity to be a faulty mapping from intensity to intensity. I consider processes that map intensity to code value, processes that map code value to code value, and processes that map code value to intensity. In my model, nonlinear processing is handled easily.

Timo uses the term "intensity level." That term could potentially be applied to nonlinear coding: consider the intensity that is associated with each level (say from 0 to 255). I prefer to use the term, "code" (or perhaps code level or code value). My term avoids implication of a proportional relationship to intensity. But when reading Timo's documents, you have to be aware that Timo's term "intensity level" implies "intensity level directly proportional to intensity."

Timo thinks that an image reproduction system should reproduce intensities physically-correctly. He wants "gamma" of unity, everywhere. I suppose he discounts film gamma - he certainly never mentions film gamma among his pages.

Main thread:

Timo thread:

See also: Gamma FAQ - Linear and nonlinear coding - Timo and linear coding

Charles Poynton
Copyright © 1998-03-12