Thanks for the comprehensive explanation.
Yeah, that was a good one. Thanks!
It's a bit of a laborious process getting to where you can set
separate end points for the three colours isn't it! Are there other
approaches to removing colour casts from faded slides with Vuescan?
You can try the auto thing vuescan does in the filters tab, just after
the "crop" tab. There is a checkbox in there for "restore fading"
IIRC.
I don't use that, though.
The approach on
www.scantips.com looks straightforward but to do it
with Vuscan looks somewhat difficult.
Well, the problem with any post-vuescan adjustments is that
in most cases you'll be working with 8-bit colour images
rather than 16-bit: do a lot of colour adjustments and I can
virtually guarantee you'll get banding and other problems.
this is because 8bit colour doe snot have much roon for a
lot of adjustment. It's good for minor colour casts but not for
major restoration work.
The approach I use is slightly different:
I save all output from vuescan as raw scan files at 48-bit depth,
full rez - this is only until I sort out the colour balance, after that
for disk space reasons I either back these up to cd or drop them.
Then I preview these files with vuescan, at 1200 or even 2400ppi
preview rez, neutral colour setting. This lets me zoom-in to the
preview and get a darn good idea of what I need to do in terms of
colour adjustments. The next step is to pick auto-levels and see
what it does. If that is not enough, I then use the inividual colour
controls, black and white point controls and such in the auto-levels
option to fine tune.
The output re-scan is then saved as a 24-bit (8-bit colour) base
image which is the start point for any further manipulations such
as cropping, rotating, sharpening, what have you. Most of the major
colour restoration is now done, so there is little danger of any colour
"after effects".
Works for me.