[argyllcms] Re: "gamma key" Re: Photocamera calibration questions
- From: Yan <yan@xxxxxxxxxxxxxxxxx>
- To: Graeme Gill <argyllcms@xxxxxxxxxxxxx>
- Date: Tue, 24 May 2011 13:12:56 +0400
Здравствуйте, Graeme.
Вы писали 24 мая 2011 г., 2:41:57:
> yan@xxxxxxxxxxxxxxxxx wrote:
>> 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.
> There are several paths available to you. You could code it
> in C using (Argyll) icclib. You could probably do it even
> easier using lcms, and lcms may have scripting interfaces available
> if you want to use something other than C (ie. lcms-python, tcllcms etc.).
>> Coolproof in matrix+gamma
>> mode reads ".ti3" values and try to
Hello,
Sorry, english is not my native. By "guessing" I mean "finding best
by calculating", of course. I understand, the this is not a
result of "random" function.
Anyway, the quesion is - do you want "colproof" to be better tool for
profiling cameras, or not. If it's not your foreground task, so, I
have to write some tool by myself :-(
>> 1. Guess gamma values;
> No, it doesn't do any guessing. If fits a response
> curve to the device behaviour exemplified by the .ti3 data points.
>> 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.
> This is what I mean by colprof not being the ideal tool. It fits
> the profile to the data as given, using a least squares type
> fit criteria.
> One workaround would be to process your data values to be
> linear light and then use the -am option to fit the matrix only. You
> would then have to patch the profile and change the gamma value
> in the R,G & B curve tags to be the gamma you know it to be.
> Graeme Gill.
--
С уважением,
Yan mailto:yan@xxxxxxxxxxxxxxxxx
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