[argyllcms] Re: help with camera profile

  • From: Iliah Borg <ib@xxxxxxxxxxx>
  • To: argyllcms@xxxxxxxxxxxxx
  • Date: Wed, 25 Jul 2012 13:20:45 -0400

On Jul 25, 2012, at 1:01 PM, Ben Goren wrote:

> On 2012-07-25, at 9:37 AM, Iliah Borg wrote:
>> You are editing in the output space, CIE. No, that is not how photography 
>> works ;) We use density calibration to control output.
> Only if you're one of those ancient fuddy-duddies still painting with 
> charcoal on cave walls!

Yes, that is me. One needs to read Kodak classic books carefully to see why it 
is the preferred way; and probably talk to some of Kodak folks before it is too 
late :(

>> 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.

> Barring, that, could you expand a bit on the monochromator / light sphere / 
> photodiode path? Assuming, of course, that that's something within the realm 
> of a mere mortal without access to a well-equipped R&D lab....

It is a bit of typing, quite a bit. May I suggest Edmund Optics or one of many 
other companies - they have the necessary equipment, and consultants to help 
you with the setup. Expect some expenses, of course.

>> Look at characteristic curves, they state density for the exposure, and do 
>> not care for colour. Colour is the second step. The error most are making 
>> when trying to imitate film in raw processing is that they do not realize 
>> the curves are not taking colour into account.
> 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.

>> 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).

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

Linearization over green, applied to all channels.

>> 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.

Iliah Borg

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