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RE: filmscanners: LED Illumination for Film Scanners



Austin wrote (re selective burning w/film scanners)

>If you could make it very very dense and were able to calibrate it somehow 
>(which is an big task in and of it self to calibrate a 2d area this size 
>with sufficient resolution), possibly, but I believe it won't work very 
>well in a real implementation.  You have to diffuse the LEDs in order to 
>make them illuminate evenly, but in doing so, individual LED coverage will 
>overlap substantially, as well as their area of coverage becoming larger. 
>This means your area of control becomes much smaller.

I think you may be unnecessarily complicating the problem. Let's say 
software and the scanner driver could control what areas were exposed, and 
for what duration, in selected areas. This would be the equivalent of the 
darkroom technician's "Dodge & Burn," but would occur during the scan.

A common problem is the photo with deep shadow and very bright highlights. A 
scanner with DR 3.3 will screw one end of the histogram or the other in this 
case, just as the film did. With selective exposure, the operator could 
select one area or another for a different exposure rate from the scanner. 
On balance, you'd have DR 3.3 in the highlights and DR 3.3 in the shadows, 
but they would have different DMin/DMax values in the selected 
areas--different white/black points, so to speak. Do you see what I'm 
getting at, here?

I'm not a good enough programmer to do such a thing, but given controlable 
variables in a scanner--which some now in fact have--it sould be done. 
Whether it's done with LED's or head speed is immaterial, it's doable.

Just another idea from the Rust Belt.

Best regards--LRA

>
> > Moreno wrote:
> > >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.
> >
> > This is a very signifficant "AhHa!" IME. I'm actually surprised that no
> > programs, to date, are using that possibility. As I might have
> > said sometime
> > ago, we users *do* have some ideas worth considering, from  time to 
>time.
> > ;-)
>
>If you could make it very very dense and were able to calibrate it somehow
>(which is an big task in and of it self to calibrate a 2d area this size
>with sufficient resolution), possibly, but I believe it won't work very 
>well
>in a real implementation.  You have to diffuse the LEDs in order to make
>them illuminate evenly, but in doing so, individual LED coverage will
>overlap substantially, as well as their area of coverage becoming larger.
>This means your area of control becomes much smaller.
>

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