[filmscanners] RE: rebuild your scanner and get better results

["Austin Franklin" <austin@darkroom.com>]

Andras,

> > Why would it be "technically very difficult to make it [LED intensity]
> > variable"?  I believe the Nikon 8000 varies the LED intensity.
>
> 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.

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"...

> As a matter of fact, the entire Nikon Coolscan line has
> fixed-intensity LEDs, as one can conclude from reading the programming
> specs (which aren't public).

As I said, I don't believe that's true of the 8000.

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
illumination.  I'm not really sure how they avoid this.  I'd almost say they
have to adjustable for calibration, in order to prevent this.  Since they
overlap, that may cause issues with simply calibrating the acquired sensor
data.  I'm not quite sure about this, but though LEDs seem like a
potentially good idea, I'm not quite sure they really pan out in the wash.

Austin

----------------------------------------------------------------------------------------
Unsubscribe by mail to listserver@halftone.co.uk, with 'unsubscribe 
filmscanners'
or 'unsubscribe filmscanners_digest' (as appropriate) in the message title or 
body