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RE: filmscanners: Link to Nikon 8000 banding example...
Can anyone give a reasonable explanation of how resonance can manifest it
self in the actual data from the scanner being incorrect? Resonance
certainly could cause micro distortion, but that is not what I believe we're
seeing. I'm not convinced it's resonance, but certainly can't rule it out.
I believe this is an analog manifestation. My guess is it is either in the
analog gain of the CCD, power supply/grounding of the CCD or A/D (causing
conversion offset problems) or the illumination.
I believe these are negative scans that people have used for banding
examples. Can someone scan a positive and show the banding to see if it
gets lighter, instead of darker?
For negatives, clear on the film represents black, and will give higher
numbers, and black on the film is white or will give low numbers. When it's
inverted, white is high numbers and black is low numbers. The banding in
the image appears to be pixel values are darker. This would mean a higher
value out of the A/D in the scanner.
People have said that it appears that the problem isn't consistent. I would
tend to suspect a grounding problem then. Does there seem to be a
temperature component to this, ie, if it's cool, does the problem manifest
it self, and warm, not? Material will, of course, expand when warmed, and
contract when cooled.
It could also be a ground loop... As a thought, try floating the scanner
(using a two prong A/C adapter), and see if that affects anything. Also,
the SCSI cable, if not made correctly, can cause ground loops...