[argyllcms] Re: Camera profiling with bracketing

  • From: Iliah Borg <ib@xxxxxxxxxxx>
  • To: argyllcms@xxxxxxxxxxxxx
  • Date: Thu, 24 Feb 2011 07:42:23 -0500

On Feb 24, 2011, at 3:45 AM, Nikolay Pokhilchenko wrote:

> Thu, 24 Feb 2011 18:29:09 +1100 Graeme Gil wrote:
>> Nikolay Pokhilchenko wrote:
>>> I'll be happy if Argyll will work with bracketed targets too. I had compute
>>> combined target in OpenOffice scalc.
>>> The bracketing is usefull for digital camera profiling, mostly in
>> highlights.
>> You'll have to explain a bit what you mean by bracketed targets. By
>> this do you mean something similar to HDR capture, where you take
>> several shots at different exposures, and then merge them back into
>> a single photo/chart ?
> Yes. I'm taking several shots of the same target under the same illumination. 
> For example, aperture values from 2.8 to 
> 11: 2.8, 4.0, 5.6, 8.0, 11 with fixed shutter speed.

First, I determine centred exposure so that the white patch is rendered to 242 
Green on rgb scale of 0..255 with gamma 2.2. Next I calculate how much up in 
exposure should I go for darkest red and blue patches turn to readings of 242 
in respective channels for same gamma 2.2. Next I calculate how much down in 
exposure I need to go to render the same patches to a value of 5 in respective 
channels. Next I shoot all the series of exposures 1 stop between the 

Iliah Borg

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