[argyllcms] Re: "gamma key" Re: Photocamera calibration questions
- From: yan@xxxxxxxxxxxxxxxxx
- To: <argyllcms@xxxxxxxxxxxxx>
- Date: Mon, 23 May 2011 13:39:07 +0400
Hello! This would be answer to question 1
I understood, that
coolproof is not the ideal tool to create profiles from raw sensor. In
fact, it's the only one.
When you write "by hand" you mean, that I
need to write another tool by myself. Of course, it's kind of an aswer
:-) But this is rather hard thing. And, on the other hand, I think that
only slighter code changes are needed.
Coolproof in matrix+gamma
mode reads ".ti3" values and try to
1. Guess gamma values;
2. Find
matrix for this gamma.
The only key I need is "not to guess gamma
upon ti3 values, and assume gamma is [some value]". The linearity of
camera sensor is quite a good assumption. By analizing this or that real
data you get "gamma 2.18" or "gamma 2.21", and this number would be not
exactly 2.2 only beacause of camera noise.
> yan@xxxxxxxxxxxxxxxxx [1]
wrote:> 1. IS IT POSSIBLE TO SET "GAMMA 2.2" IN INPUT FOR COLPROF
UTILITY SOMEHOW, NOT BY MAKING A LOT OF "AUXILIARY COLOR CHARTS"?
> Hi,
I'm not quite sure what you mean by this. colorprof creates a profile
that represents the behaviour of the device as sampled by the .ti3
values. You can't "force" the profile model and expect it to be a good
fit to the samples. There is no point in doing such a thing - the whole
purpose of a profile is to represent the color behaviour of the device.
colprof is not the ideal tool to create profiles from raw sensor data
that's been converted to samples, since it is doing a "best fit". You
are probably better off creating a matrix and curve model "by hand".
Note that you (ideally) need both the spectral sensitivity data, and the
response data for each sensor. The curves should then translate the
sensor responses to linear light, and the matrix convert to XYZ space
>
> Graeme Gill.
Links:
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