Ralf Schmode wrote:
> as you may remember, I addressed this list two weeks ago because my
> freshly delivered Minolta Dimage Scan Elite II turned out to be
> defective right out of the box (banding and "telephone wires", see
> for details).
I've just got an Elite II and have been checking the deep shadows for
issues, particularly the red channel banding. I have noticed something
very odd. A straight scan (with or without ICE) shows red channel
banding identical to what Ralf got along with some "telephone wires".
However, when GEM is enabled, the banding pretty well disappears.
And it also looks like some of the the other CCD anomalies like the
"telephone wires" also improve or disappear.
As far as I can tell, the Minolta implementation of GEM writes the whole
scan to the hard disk and then manipulates the file to generating the
final version. The whole process obviously takes longer than a straight
scan but the actual scanning speed within it looks much the same.
Also, when GEM or ICE are switched on or off, some of the calibration
files (in particular "dark.bin") are updated as part of the preview
process. (The software generates 4 white and black point calibration
files when it first connects to the scanner, plus a 5th for IR once ICE is
switched on.) The disappearance or reappearance of any "telephone
wires" anomalies seems to co-incide with any updating of these files.
This seems to suggest that the banding (or lack of it with GEM) is not
caused by any change in scanning speed (or anything else mechanical)
but by a glitch in the calibration, which doesn't occur with GEM. Or
alternatively, the algorithms in GEM are just good at cleaning up these
sort of deep shadow problems......
I suspect the issue is faulty calibration by the software (maybe made
worse by poor QC) rather than it being purely hardware. Could well be
good hardware let down by buggy software or firmware.
I haven't reached any conclusions yet whether what I've seen will
constitute real problems in normal scans. Certainly, using GEM and x4
multiscanning on one of my (underexposed) slides I use as a test and
pulling up the shadows, the result was far better than my old Elite. Now
all I need to do is work out the particular workflow and combination of
settings which give consistent and equally good results :)
Incidentally, it doesn't look like the current support for the scanner in
the latest version of Vuescan incorporates calibration routines. Pity
really, as this would help clarify whether the hardware or the Minolta
software is the issue.
Al Bond
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