[argyllcms] Re: help with camera profile

  • From: Ben Goren <ben@xxxxxxxxxxxxxxxx>
  • To: argyllcms@xxxxxxxxxxxxx
  • Date: Wed, 25 Jul 2012 10:46:39 -0700

On 2012-07-25, at 10:20 AM, Iliah Borg wrote:

>>> Colour is a given, it is defined by the set of dies, pigments, colour 
>>> filters in front of the sensor. It is easy to determine the spectral/colour 
>>> properties of a CFA - all you need is a rather cheap monochromator, a light 
>>> sphere, and a reference photodiode ;) Or, some inside information from the 
>>> manufacturer. Or, some red, green, and blue patches to shoot.
>> Would the red, green, and blue from a ColorChecker work *well* for what 
>> you're describing?
> They work quite well.

In that case, considering the expense of acquiring new equipment...could you 
point me in the right direction? If I wind up unsatisfied using the 
ColorChecker, then I can always give Edmund Optics a call at that point.

>> I know there are those here looking to imitate film
> It was just an example. For me, it is not about imitating, but about the 
> preservation of the culture which is going south.

Film is a wonderful artistic medium. It damned well better be, considering 
everything that people have put into it over the years. And it's no more going 
away than painting on cave walls with charcoal...though it (and, of course, 
eventually digital photography also) will wind up as uncommon as cave painting 
at some point.

I'd think that, by now, we should be getting to the point that a dedicated 
amateur chemist should be able to make emulsions in a home lab, though 
certainly not as cheaply as in a dedicated factory. Perhaps now would be a good 
time to recruit some of those Kodak (and Fuji, etc.) engineers to such a cause?

>>> This would be my wish list: First, equalization of light based on the 
>>> target border (includes white balance and light un-evenness).
>> Robin Myers's EquaLight does a superlative job of that, but it only works on 
>> TIFFs.
> Raw is a tiff, actually, for many cameras. We are not profiling over raw data 
> in any case, and I do not see any reason why that would be beneficial. When 
> I'm saying "white balance" I mean equalization gradient of the balance across 
> the shot, as it deviates due to light sources being not exactly the same 
> (your setup includes 4, if I remember correctly).

Then, yes. Equalight does exactly that type of white balance, and does it 
superbly. You do remember correctly about my setup, and I'm pleased to report 
that there basically isn't any deviation due to uneven illumination, but there 
(of course) *is* the typical peripheral transmission falloff of the lens (aka 
``vignetting'') in captured images. And Equalight transmogrifies the TIFF such 
that it appears that I've used a perfect, vignette-free lens.

>>> Second, linearization using the grey step wedge.
>> Would such linearization apply equally to all channels?
> Linearization over green, applied to all channels.

Sounds like it winds up being pretty much logically equivalent to what I've 
been doing.

>>> Nothing is particularly hard if you divide it into small jobs (c) Henry Ford
>> ...until you wind up with so many small jobs that managing them itself 
>> becomes a big job....
> Well, I feel comfortable with my workflow. It is just some script processing.

Any chance you'd be willing to share details? I've scripted out parts of the 
workflow, but so much so far has been done with pointy-clicky programs or I've 
been refining the workflow so often that I still wind up doing a fair amount of 

Thanks again,


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