> > I have an Acer ScanPrisa 620 UT. It works, but the RGB offsets are noticeable.
>
> Maybe the overhead (transparency unit) lamp *needs* special
> calibration? The manual for the Prisa 620ST states that when
> scanning slides or negs you must use the supplied mask and you
> must leave the calibration window in this mask unobstructed.
Yes, that's correct. And of course I'm using the mask in transparency mode. I
have the impression that the calibration is done by the firmware - at least the
trays move to the calibration area before each scan.
The offsets appear in flatbed and transparency mode, though.
However, the RGB offsets as I understand them are not an offset in value but a
spatial offset. E. g. if you scan a black square on white background in
color mode it doesn't have sharp edges but maybe a blue edge on one side and an
orange edge on the other. Just try it.
Oliver
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