[argyllcms] Re: Camera profiling with bracketing

  • From: Graeme Gill <graeme@xxxxxxxxxxxxx>
  • To: argyllcms@xxxxxxxxxxxxx
  • Date: Fri, 25 Feb 2011 13:43:46 +1100

Rishi Sanyal wrote:
Don't know if this'll help or is relevant, but when I experienced
flare in IT8 target scans due to scanner optics, the flare was
generally dependent on how light the patch to any side of a patch in
question was (the light the patch, the more light that bled onto an
adjacent patch).

Yes, that is to be expected. It's a difficult to avoid, unless you
make a chart with well spread test patches on a matt background.

So what I did, manually, was to take such problematic patches, select
them using the marquee tool, then copy&  paste over the original patch
rotated 90º using the 'darken' blend mode in Photoshop. I did this
also for 180º&  270º for each patch. This got rid of flare on most
patches&  resulted in a profile that showed less clipping of dark
colors (since flare artificially brightened a lot of dark patches,
which the profile tried to compensate for by darkening those colors).

I guess this could be automated by looking at the spread of values
over a single patch, and just choosing the darker values, but it's
equivalent to using smaller patches, with all the disadvantages that

Another approach might be to try and characterize the inter-patch
flare for a particular chart layout, but this wouldn't account
for all the sources of flare.

Graeme Gill.

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