Re: filmscanners: LED Illumination for Film Scanners

["Moreno Polloni" <mp@dccnet.com>]

> > 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.
>
> I doubt it.  The control isn't that fine since the array is so course.
Also
> it would make the unevenness worse.

Notice my words, I said to "some" degree. This isn't much different than a
contact printing box made up of a dozen or so incandescent lamps that can be
individually switched on or off. In which case you are purposely seeking
uneven illumination.

> > With an appropriate control mechanism, a user could
> > adjust for dead even lighting across the easel for a specific
lens/format
> > size combination.
>
> Not with that array shown, and not without a VERY diffuse diffuser.
Making
> an LED array as shown is not a high level of sophistication.  If it truly
> worked well, I would believe that it would be being used by the enlarger
> manufacturers, or at least offered in the aftermarket.  I don't believe
> either is true, or does anyone know differently?

I said "dense LED array". The degree of sophistication in that enlarger
light source was with the control electronics, and high-output LED's with
very tight spectral parameters. It provided a very precisely controlled,
low-heat light source that seemed ideal for enlargers. The downside, and
probably one of the reasons there was no commercial development, is that the
high-output LED's were very expensive at the time, and given the shrinking
high-end enlarger market, probably not too much hope of commercial success.

> The use of an LED array as a light source for a film enlarger is entirely
> different than using an LED array for a scanner, where you have individual
> sensors that you can adjust to accommodate for the unevenness of the LEDs.

How have you determined that the LED's are uneven?