Re: filmscanners: LED Illumination for Film Scanners

[Isaac Crawford <isaac@visi.net>]

Austin Franklin wrote:
> 
> > Austin Franklin wrote:
> > >
> > > > 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.  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.
> >
> >       All that you would need to do is shoot this array through
> > some sort of
> > diffusing device.
> 
> And that was the question, was there a diffuser of some sort, and that has
> gone unanswered.
> 
> > After all, light bulbs aren't exactly evenly
> > illuminated and those have been used for years in enlargers...
> 
> Yes, and incandescent light bulbs used in an enlarger get a condenser
> system, which is entirely different than a cold light head, which is
> basically what most scanners use for illumination.

        Well halogen bulbs have the same uneveness problems as regular bulbs,
but with the use of a mixing chamber, they can give the same results a
"cold" head can... I can see some potential advantages in an enlarger
with LEDs in this arangement, primarly concerning heat. I'm not sure
what sort of advantage LEDs would have in a scanner, maybe long life
with minimal shift (light wise)?

Isaac