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Subject: Re: ACR Calibration

Rags Gardner wrote:

> Unit to unit differences should be minimal. <<


> It is impossible to design any sensor that realistically matches CIE
XYZ or CIE RGB. These are derived color matching functions based on human
psychological responses (psychophysics), not a sampling of physical devices.<<

Please see:

Chris Cox wrote:

> You can make XYZ filters for electronic light sensors (some display
calibrators have done so).<<

Thomas Knoll wrote:

> Actually, to create a camera filter set that is "perfect", it is not
required to exactly the match the human cone responses (or the XYZ responses).
All that is required is the filter responses be some linear combination
of the human cone responses. If that is the case, then a simple 3 by 3
matrix can be used in software to recover the exact XYZ values.

If the filter set is not a linear combination of the cone responses (which
is the case for all current cameras), then any color calibration is going
to be some kind of comprise, getting some colors correct and other colors
incorrect. This is true even if you know the exact illuminant spectral
curve and the exact filter spectral response curves. <<

Best regards, Peter



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