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[filmscanners] Re: Difficult scan problem

On Mon, 15 Apr 2002 11:06:59 +1000  Op's (martin@wollongong.apana.org.au)

> I have suggested that tranny film is used in place of neg material but
> photographic prints
> are some times required.
> Can anyone suggest another technique that will give me a closer colour
> scan than what I'm
> getting now.

You are unlikely to get a decent colour balance in this situation direct
from scanner software. If you can do it in PS, using the black, midtone and
white eyedropper samplers in 'levels' should do this well.

Since you are using (presumably) constant colour temp lightsource and
exposure you can create a set of correction curves which will be useable
for all images, but you will need to shoot a reference neg which includes a
neutral mid grey, black (Dmin on the neg) and white (Dmax on the neg).

You can probably get the black and white points from one of your existing
images but the neutral grey may be tricky - probably shooting an ND gel
would be closest. Don't worry about it being exactly 50%/1 stop/OD 0.3 -
you can always change the overall gamma as necessary after applying the
colour correction. However, if you have photographed any decently
monochrome crystals - soda? salt? sugar? which produce a full range of
tones, that image could act as your calibration slide.

Note that you don't have to set the dropper values to be neutral, you can
bias them toward the illuminant colour of the microscope if that looks more
acceptable (double-click each dropper tool, select the target colour and


Tony Sleep
http://www.halftone.co.uk - Online portfolio & exhibit; + film scanner info
& comparisons

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