Major A wrote:
> Does the halo only appear along one direction, or evenly in all
> directions around the highlight? Since film scanners only use one CCD
> line, this leaking can obviously only take place in on direction.
Hi, Major,
yes, you're right. I remember the halos to be in each direction, meaning
it can't possibly be sensor crosstalk.
>>2. Film surface. Slides have a texture on their surface, following the
>>outlines of the subject that is on the slide. I am positive that the
>>thickness of the dye layers in these areas varies with this texture.
>>"Jumps" in dye layer thickness are likely to cause diffraction of the
>>
>
> The thickness has no more effect that the density variations. As long
> as the texture is thinner than the features of the picture (which is
> the case), it has no influence on diffraction.
I have seen Sensia slides which the texture could not only be *seen* but
even *felt* on. I am not sure those are in any case thinner than the
picture subject's outlines.
> Then, however, you should also see a halo under the microscope or with
> a (condenser) enlarger, or even with a slide a projector.
Theoretically, I'd agree but I've seen slides under a microscope,
scanned and in projection and the optical appearance was different for
each type of visualization including "features" such as scratches, dirt,
grain and halos. The method of illumination is different, so is the type
of "sensor" (CCD, eye) being used.
> I think the problem is flare within the scanner. In the case of the
> Nikons at least, I'm sure it is caused by dust, because their optics
> are damn good.
I have seen three new Minolta units and two new Nikon units showg only a
marginal difference as to this issue. Flare may be a reason (though hard
to believe), dust should be almost impossible to be blamed with brand
new units.
Greets -
Ralf
--
My animal photo page on the WWW:
"Best of" portfolio:
Find my PGP keys (RSA and DSS/DH) on PGP key servers
(use "TrustCenter" certified keys only)
----------------------------------------------------------------------------------------
Unsubscribe by mail to listserver@halftone.co.uk, with 'unsubscribe
filmscanners'
or 'unsubscribe filmscanners_digest' (as appropriate) in the message title or
body
