[argyllcms] Re: Profile input white not mapping to output white

  • From: Ben Goren <ben@xxxxxxxxxxxxxxxx>
  • To: argyllcms@xxxxxxxxxxxxx
  • Date: Fri, 23 Nov 2012 09:50:44 -0700

On 2012-11-22, at 8:25 PM, Iliah Borg wrote:

> Additionally, I see clipping of the green channel on the portions of the 
> whitest patch of the target itself

I just looked a bit closer, and I can only see a half-dozen pixels clipped in 
the second green channel in patch N18, and they're all outside of the 
BOX_SHRINK margins. There's a fair amount of clipping in the white balance 
target on top of the chart (a piece of Tyvek), but I'm only using that for 
white balance -- and, of course, I'm not getting the white balance from the 
clipped portion.

> and general clipping on the darkest patch.

Actually, that's a good sign. That's a light trap; the entire target is a 
one-inch-deep hollow box lined with black flock velvet, and that patch (I13) is 
a hole cut in the top of the target.

> Shooting against bright background for profiling may add unwanted flare to 
> the shot. I recognize that those are your actual shooting conditions, still I 
> would try to profile from a shot with a dark background and see if it helps. 
> It certainly helped in a test I just made.

Hmmm...I can try turning off the background lights for the profiling 
shot...still, they're contributing a fair bit of illumination to the overall 

> Last, but not least - raw converter you used seems not fully adequate for the 
> task as it treats highlights in a slightly crude manner.

Said converter is RAW Developer, which is supposed to use DCRAW for its 
processing engine. I think it does have some different options for highlight 
recovery...I'll see if tweaking those knobs makes any difference.


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