On Tue, Nov 16, 2010 at 10:54:13PM +0100, Pascal de Bruijn wrote:
> On Tue, Nov 16, 2010 at 10:45 PM, Bruce Guenter <br...@untroubled.org> wrote:
> > On Tue, Nov 16, 2010 at 06:08:48PM +0100, Pascal de Bruijn wrote:
> >> I'm pretty sure this is not really how it works...
> >> [snip]
> >> A consistent difference in exposure, is usually not a difference in
> >> exposure, this is usually just a basecurve difference. In UFRaw you
> >> can emulate this either by fiddling with gamma/linearity, or by making
> >> a nice basecurve for your camera...
> >
> > Thanks for the tip on the curve. I had already played around a lot with
> > gamma/linearity but that didn't help. Using a base curve I've come
> > closer to the camera's output than with a straight exposure
> > compensation, but it's only really visible in the highlights. All but
> > the top end of the curve is very close to a line of slope 2 (the same as
> > a +1 exposure compensation). The colors aren't quite exactly the same,
> > but I'll blame that on minor differences in the color matrices.
> >
> >> I while back I did a basecurve for my Canon, like so:
> >
> > I put mine up if anybody else with a Sony A700 is interested:
> >
> > http://untroubled.org/ufraw/a700.curve
> >
> > Would there be any interest in some way of auto-tuning a curve from a
> > collection of raw+jpeg images?
> >
> > This actually brings up another point, though. I process raws from two
> > different cameras, which will need radically different base curves.
> > Switching back and forth on each photo is going to be a royal PITA. The
> > only way I can currently see around this is to save the config at the
> > start of each batch.
>
> Actually this curve seems to be quite charactistic per _vendor_, not
> really per camera... At least if you discount really really minor
> changes.
>
> I've got basecurve for most camera types in Darktable already.
>
> > Is there any plan to support multiple profiles? I heard hints of it a
> > while back, but nothing has materialized that I've seen. If I decide to
> > take a try at it myself, are there any suggestions how to approach it?
>
> These basecurves should be interchangable with any matrix-only profile.
Where do these basecurves come from and how do I calibrate my own?
> Pascal de Bruijn
slainte mhath, RGB
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