Austin,
> > LED intensity is hard to control without feedback because their
> > response of intensity to voltage and current isn't linear.
>
> That really doesn't matter, as it is then calibrated...so there IS feedback,
> per se.
OK, but calibration is only done for one intensity -- the scanner only
stores one value per pixel as calibration data (not even one for each
colour channel).
> BTW, it appears you didn't mean it's technically difficult to make the LED
> variable, as it really isn't, but that it's more difficult to do it with
> "accuracy"...
OK, that's what I meant. To maintain colour balance, however, you have
to control the LEDs pretty accurately.
> One of the issues with having multiple light sources, as these LED light
> sourced scanners do, is that the light sources do overlap (they have
> to)...and this can cause banding problems more so than a single
No, they don't overlap. LEDs emit a very narrow band of light (in
terms of frequency/wavelength), and the bandwidth is much smaller than
the separation of the LEDs (few nm as compared to few 100 nm).
How would this cause banding, BTW?
Let me put it this way: there is a way of setting exposure times for
all colour channels (except IR) on Coolscan scanners, but there is no
setting for LED intensity. The LS-8000 is no exception.
Andras
===========================================================================
Major Andras
e-mail: andras@users.sourceforge.net
www:
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