> That is a bad design in my book. You can get banding by doing that, as well
> as inaccurate color. They SHOULD have calibration for all three colors,
> whether it's the light source that changes for each color, or they use a
> tri-linear sensor...or in the case of the 8000, they do both I believe.
Calibration for all colours is not necessary, and lack of it doesn't
cause banding. The problem in the LS-8000 is that only one of three
CCD lines is calibrated.
> I'm not a fan of LED light source, and I believe the 8000 uses a monochrome
> tri-linear sensor, and changes the color of the light source and takes three
> exposures per line...and as I said above, not calibrating, and providing
> calibration correction for, each line of the tri-linear sensor by it self
> can lead to banding...and apparently that's what was discovered as the cause
> of banding on the 8000.
True. The LS-8000 exposes all three lines with the same colour at a
time, thus banding has nothing to do with the differences between the
different LEDs.
> I don't quite know what you are saying above...as LEDs have a rather wide
> angle of dispersion, and that really has nothing to do with the
> frequency/wavelength. I'm talking about physical coverage, not
> frequency/wavelength. Again, I don't believe there is a physical light gap
> between adjacent LEDs. If they did, as I said, then there would be gaps in
> the illumination...even with a diffuser, the middle area would have slightly
> degraded illumination...and as I said, that could cause very noticeable
> banding.
Ah, OK, illumination only affects colour balance along the x direction
of the scan, can't cause banding (in the y direction, that's where
banding occurs).
> We should possibly ask Ed Hamrick about that, but needless to say, I'm
> skeptical as far as the 8000 goes. Though you may have "a" scanner
He doesn't know more than I do, he has the same documentation. I not
only have documentation but have also had contact with Nikon's
developers.
My points are these, I'm absolutely sure about these and not going to
argue any further:
- banding is caused by the failure of the LS-8000 to calibrate three
CCD lines separately, and has nothing to do with the illumination.
- the LS-8000 has fixed-intensity LEDs, and there's no reason to run
LED sources at anything less than full intensity anyway.
You may disagree, of course.
Andras
===========================================================================
Major Andras
e-mail: andras@users.sourceforge.net
www:
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