[filmscanners] Re: Defective Minolta Dimage Scan Elite II: update :-((

["" <al@greenspace.freeserve.co.uk>]

Ralf Schmode wrote (on the cause of the red channel shadow banding
disappearing when GEM is turned on):

> You may find out by using GEM at a very low value (1 instead of the
> default 50). If it is the cleaning effect of GEM, a value of 1 should
> leave more of the banding than a value of 50. If it is just a matter of
> the calibration data being re-written, the banding should be gone even
> at a value of 1 (which I doubt will remove any grain at all).

Good idea and I've just tried it.  With GEM set to 1, the banding is
improved but still definitely there.  Set to 0, the banding is (not
surprisingly) the same as when GEM is turned off.  So it seems to be
GEM (rather than recalibration) which gets rid of the banding.

On the other anomalies, GEM improves them as well but doesn't get rid
of them completely.  There seems to be less consistency as to what
settings make them appear (and disappear) but recalibration does
seem to enter into it.

GEM does work very nicely on some images but, as you say, it wouldn't
be appropriate to use it all the time.

> I may be mistaken but as far as I know *every* CCD unit would be
> "faulty" in the sense of showing off "telephone wires" without prior
> calibration. What I am not sure of is, for example, if a single CCD
> pixel lost "efficiency" in the sense of electrical response to light
> exposition (as a result of aging, dirt, you name it), whether or not the
> Minolta Software would be able to correct this properly.

Good question - maybe the next version of Vuescan will help answer this.



Al Bond

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