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Re: filmscanners: LED Illumination for Film Scanners



> > A couple of years ago someone on the darkroom newsgroup was working on
an
> > LED light source for enlarger heads, utilizing clusters of
high-intensity
> > LED's. I don't know what happened to the project, but at the time a lot
of
> > people were really excited about the technology and the initial results
> > showed a lot of promise.
> >
> > http://www.trailing-edge.com/www/led.html
>
> Yes, and look at how uneven the lighting is.

Quoting a recent post on this list: "And you can tell this from a 72dpi JPEG
image?"

> For an enlarger, that may turn
> out to be a very bad idea, simply because you can't adjust each individual
> LED for even illumination.  At least with a CCD, you can adjust the gain
for
> each sensor element to get even illumination.

Why can't you adjust each LED for illumination levels? For instance, the
designer could quite easily vary the voltage levels throughout the array to
compensate for enlarger lens light fall-off. And taking things one step
further, a dense LED array positioned closer to the negative could even be
programmed to provide some degree of selective dodging/burning/variable
constrast control. With an appropriate control mechanism, a user could
adjust for dead even lighting across the easel for a specific lens/format
size combination.




 




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