Thanks, Art. So as I see it from your diagram, there *could* be a light
fall-off outside the areas seen most clearly by the lens. I don't know how
that would be measured, but with the Yellow Stain phenomenon, it's clearly
in Kelvins, since it goes to yellow from what should properly be blue, but
does not approach red in anything I've seen (although if "red" were there to
begin with, it would be darkened).
I'm not offering this as an expert--I'm just trying to understand it. So
far, most of the input makes sense. A light drop-off will normally affect
the red part of the spectrum least, and blue part most.
Best regards--LRA
>From: Arthur Entlich <artistic@ampsc.com>
>Reply-To: filmscanners@halftone.co.uk
>To: filmscanners@halftone.co.uk
>Subject: Re: filmscanners: Stains and Grains (was Yellow Stain)
>Date: Sun, 08 Jul 2001 03:06:43 -0700
>
>
>
>Lynn Allen wrote:
> >
> > Hi Frank,
> >
> > OK, then that would mean that the sensor array is vertical to the line
>of
> > travel, and the scan is horizontal, as we thought, and that makes sense.
>Now
> > optics *could* cause light drop-off, but frankly I don't quite
>understand
> > how that mechanism works, either. I'd almost have to see it--and
> > conemplating that, what I *see* is a part or two left over after I've
> > re-assembled my Scanwit! ;-) (I actually *did* that with an electric
> > typewriter, once. For some reason, it still worked! :-))
> >
> > Best regards, and keep us plugged in--LRA
> >
>
>
>OK, I'm gonna try some very simple ASCII art here.
>This is how scanners which move the film work. There are others (Nikon,
>for example) which move the light source and CCD assembly and the film
>stays put.
>
>This is a cross section.
>
> _________________________
> light source (remains stationary)
> VVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVV
>
>
> ===<<<======<<<=====<<<======<<<=====<<<======FILM FRAME (which moves
> left one "segment"
> (pixel length) per
> "reading"
> .............
> ........ ........
> ... ...
> ... ...
> ... ...
> | | << LENS (remains
> ... ... stationary)
> ... ...
> ... ...
> ......... .........
> .............
>
>
> ====== ====== ====== < CCD sensors (remains
> R.CCD GR.CCD BL.CCD stationary)
>
>
>Usually either lens or CCD units move for focusing.
>
>
>Art
>
>
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