"Bill Tuthill" <> wrote in message
news:...
[re image with red cast]
> Perhaps the K100D wasn't set to auto-white-balance; most cameras aren't
> very good at AWB anyway.
AWB can be treacherous, since it relies on image data and the computer has
no idea what it is looking at. The methods used for AWB are proprietary,
but my guess is most of them toggle in a tri-modal distribution between
daylight, shade, and tungsten. In spite of being confronted with this
guessing game, no manufacturer (that I know of) makes a camera with a
built-in incident light meter / colorimeter. It would seem that that would
be useful, since it would act as a built in and unambiguous gray reference.
Evidently that does not work, since no one does it. Which should give us
pause about relying too much on neutral gray cards for color balance!
> Really, neutral dark/light make AutoLevels work well? I did not know
> that.
AutoLevels scales the values of all three channels to span the same range.
If the brightest and darkest points in the image are neutral, which is true
for a majority of images, you get a nice color cast removal. So AutoLevels
works well for the majority of images, and fails for others. AutoColor is
AutoLevels in color mode, keeping the original tonality.
--
Mike Russell
www.curvemeister.com/forum/