[filmscanners] Re: SS4000 again

["Arthur Entlich" <artistic-1@shaw.ca>]

Firstly, the reason the Minolta now comes with a filter is because I,
and a couple of other people got together and proved to Minolta their
light source was not diffused enough, and was leading to problems with
dust and scratches and such causing major headaches.  In fact, it
happened because a private individual started selling diffusers for the
Minolta Pro MF scanners in Holland after consulting with myself and Bo
W. in Sweden.

But more to the point, diffused light doesn't soften the image to any
significant extent.  What it does do is reduce the visibility of surface
defects, and somewhat, grain edges, which gives the perception of lower
resolution because the eye tend to measure resolution by a mixture of
contrast and "landmarks".

With microscopes you are correct, because the thickness of the specimen
is often many times more than the thickness of the image emulsion layer
of film.

In terms of film, however, probably the only way to prove this to you
would be to scan using a resolution grid, and see if the counts are
different with the two light sources.

Art




Bob Frost wrote:

> Tom,
>
> Surely the whole purpose of collimated light sources is to achieve maximum
> resolution (I seem to remember this from my light microscopy days many years
> ago). If you use diffuse light, you will not achieve max resolution: it's
> equivalent to blurring the image. The Minolta 5400 has a removable diffuse
> light filter, and if you switch it into position, you lose resolution, and
> the image becomes soft. You also lose resolution on the dust and scratches,
> but you can't have one without the other (as Doris Day used to sing).
>
> Bob Frost.
>
> ----- Original Message -----
> From: "HPA" <tom@historicphotoarchive.com>
>
> DIFFUSION OF LIGHT SOURCE: The Polaroid uses diffuse light, which minimizes
> dust and scratch marks on the base side of the film. The Nikon uses
> collimated light and this accentuates dust on the base side.  Of course the
> Nikon has the automatic dust removal, however that does not work with
> Kodachrome because the film is opaque to IR light.
>
>
>

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