Re: Primer on photographic exposure, etc.
Re: Primer on photographic exposure, etc.
- Subject: Re: Primer on photographic exposure, etc.
- From: Iliah Borg <email@hidden>
- Date: Wed, 15 May 2013 11:27:20 -0400
Dear Ben,
I'm just saying that C1 prefers LUT profiles, and there are 2 ways of doing it - make a matrix and convert to LUT; or make LUT directly. One can do both and keep both, they both have their own advantages.
For a minimal profile 24 patches is too little with current profiling engines, matrix or LUT, does not matter. ColorCheckerSG with its 140 patches is a far better choice. Making a combined target from 3 shots of SG bracketing the exposure by 2 stops is even better. Target needs to be individually and accurately measured, canned measurements do not fit well. Scaling for a combined 420-patch (140*3) target is easier if measurements are spectral.
On May 15, 2013, at 10:46 AM, Ben Goren wrote:
> Iliah,
>
> I know you're a fan of matrix profiles for camera input -- and for very good reason, as it's a good model for the sensor behavior and they give good performance in most conditions.
>
> But, for reproduction work, I've found that profiling the illuminant is at least as important as -- if not more important than -- simply profiling the sensor, and the only way I've found to do that is with a LUT profile built by throwing as many patches with as many different spectra as possible at the problem.
>
> I should also note: you want lots of patches and you want lots of spectra, but you don't necessarily need to serve both purposes at the same time (though that would certainly be ideal). My current chart is a mixture of paints and other things (for diverse spectra) and inkjet-printed patches (to fill out the patch count). The diverse (paint, etc.) spectra help define the boundaries and critical points and metameric challenges, while the sheer volume of (inkjet) patches provides the resolution needed.
>
> Cheers,
>
> b&
--
Best regards,
Iliah Borg
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