Filmscanners mailing list archive (firstname.lastname@example.org)
[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: filmscanners: Bad CCD elements - was Scan Dual II Bad Elements
> > Norman Unsworth wrote:
> > How do the bad elements in the CCD evidence themselves?
> However, individual pixels or CCD elements can also be defective or
> miscalibrated. The best way I have found to check for these is to use a
> slide with areas of darker colors, perhaps even a near black slide will
> work. You want something that doesn't have a lot of lines or detail in
This is all very familiar. When I got my Scan Elite 18 months ago these sort
defects were very obvious in the green channel with only very little gamma and
point adjustments. I got it repaired under warranty and it seemed much
(although not perfect) and generally usable.
However, several months later, I started to do some scans of night scenes on
Kodachrome 64 which needed the shadow detail boosted and multiscanning to
noise. That highlighted some dodgy green channel CCD elements but, more
worryingly, a shift in the whole CCD response in longer duration scans.
the black edge of the frame was returning, say, an average value of 25 in the
channel at the start of the scan, by the end of the scan it might be well over
greater the level of multiscanning, the worse it got so x8 and x16
introduced a haze over all the deep shadows across all but the first few pixels
whole frame. Certainly, there was no hint of noise but no detail either......
After many mails to Minolta UK (and the inevitable "it's been referred to Japan
haven't replied" black hole), they recently replaced the unit. It, too shows a
"lazy" green channel CCD elements but nothing too bad. It does seem to have
more noise generally than my old scanner but, as it was defective, it's rather
Anyway, if there aren't too many lazy CCD elements, they can be fixed at the
scan stage relatively easily. (The ones on my Elite seem to be due to poor
rather than being broken, with the black end response in the green channel
high hence the green tracks in the deep shadows.) After finishing adjusting
curves etc in 16 bit, convert the image to 8 bit. In Photoshop, use the single
column marquee tool, depending on orientation, to select the offending CCD
Use Select and Color Range to select just the shadows. Then, in the green
(or whatever the affceted channel is) adjust the black point in levels to so it
the neighbouring elements but keep the mid-point slider in the same position.
well, there is *no* evidence of the lazy CCD.
If there aren't too many lazy elements and the scanning exposure is relatively
constant, it should be possible to record a PS action to do this
that I've done this yet!) Of course, assuming that there is a true black
in the scan like the frame edge, what would really be good would be a bit of
which took each row (in a 16 bit raw gamma 1 file) and set black point. I know
scanner calibration process should do this but, from the problems some Scanwit
Minolta owners have had, the scanner calibration and/or software just ain't