[argyllcms] Re: Camera matrix profile, adding ti3 perfect white data set

  • From: Elle Stone <l.elle.stone@xxxxxxxxx>
  • To: argyllcms@xxxxxxxxxxxxx
  • Date: Fri, 29 Jan 2010 15:54:09 -0500

On 1/28/10, Gerhard Fuernkranz <nospam456@xxxxxx> wrote:

> But yes, given a (mostly) linear sensor, your desire may not be to fit
> systematic unknown errors in the measurements as good as possible with a
> matrix/gamma model, but you may rather want to estimate the "flare-free"
> behavior of the camera with a matrix-only model. IMO it may indeed make
> sense not to attempt to fit the flare in the measurements, but rather
> use a more constrained model which rather prevents fitting the flare,
> because flare depends on the captured scene, having a different
> intensity and color at each pixel of the image. The way how the RGB
> numbers of the patches of the target are corrupted by flare (in the shot
> of the target) is not  necessarily representative for shots of other
> scenes, with a different spatial arrangement of colors, and with a
> possibly different overall brightness of the scene.
>
> Regards,
> Gerhard
>

Hi Gerhard,

You said it much better than I could have. But that is exactly what
I'd like, if I understand you correctly. As best I can determine, the
sensor itself (plus internal camera processing and dcraw for raw
rendering) responds linearly. I want a profile that ignores all
detected variations in L* and just gives me the primaries that make
the best fit to color. I'm not looking for a profile that pushes down
the shadows to compensate for flare and such because as you say, the
necessary compensation varies with the lighting, angle of camera to
light source, use or not of a hood, brightly reflective objects in the
image, etc.

Regards,
Elle

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