Digital BW, The Print

----- Original Message ----- 
From: "Austin Franklin" <darkroom@...>
To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
Sent: Wednesday, May 21, 2003 12:52 PM
Subject: RE: [Digital BW] Digital, film, scanning comparisons


> Hi Martin,
>
> > With the drum scanners where in the light path are the color
> > filters? Are they between the PMT and the film or between the
> > light sources
> > and the film?
>
> Light path of a drum scanner:
>
> light source -> mirror -> drum -> film -> lense -> splitter ->
filter(s) ->
> PMT(s)

Austin,

Thanks for the info.
>
> > If the latter case, I would assume there is a theoretical
> > advantage in resolution to using a single color light source.
>
> Single color light source, typically a halogen or something very bright
and
> focused.
>
> > If
> > filtration
> > is after the light passes through the film than all three
> > channels would be
> > equal.
>
> The filters will make them not equal though...  What do you mean by
"equal",
> and why is that important?

My thought was that a light passing through the negative that is of high
frequency and very narrow in frequency range would result in higher
resolution in the scan since such a light would have less and more
consistant edge diffraction than say a white light source. In practical
terms this may not be significant since the quality of other elements in the
scanner might wipe out the benefit.

If the filters are after the splitter then the resolution of the three
channels should be the same if you are scanning a B&W neg, or am I missing
something such as PMT response to different colors.

Martin