Re: Gamma of Primaries

Re: Gamma of Primaries

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Gregg Loewen

hi John

A good question for Dr Rudd too….Id love to have his input.

Basically when asking about the “intensity” of the primaries at a variety of stimulus points you are correctly talking about primary gamma (vs gray scale gamma).

A good test for color decoding is measuring primary intensity at 100% stimulus then comparing it to primary intensity at 75% stimulus. If it is not in the same proportions then there is a color decoder error (which may or may not be further correctable). This is essentially measuring primary gamma response (in the color decoder).

We teach to do CMS adjustments at 75% stimulus as this is closer to the percentage of stimulus of an APL (average picture level), and thus best represents an average picture.

Hope this helped ??