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[filmscanners] Re: Strange light spill-over in Nikon LS-8000scan
That all sounds like a reasonable explanation. Thanks.
Yes, the reason using the glass carrier is because the regular one sucks
(really, Nikon should be embarrassed, and then smacked in the head for
continuing to supply the flawed item with the LS-9000 and making you pay
$250+ extra to get a carrier that actually works). However, I will try
it with the glass-less carrier and see what happens -- try to and
determine whether it is the CCD or the all those interfaces causing the
problem. However, after hours of trying to get the glass-less carrier
to properly hold a piece of film, one of the hinges/clips on the top
cover broke, so now it holds even worse than before.
Arthur Entlich wrote:
> I looked at the image you provided, but the jpeg artifacting makes it
> difficult to analyze what you are speaking of exactly.
> However, there are some knowns regarding scanning.
> 1) Blooming: high contrast areas with high brightness push the CCD
> sensor limits in terms of the amount of electrons they can handle. The
> nature and design of Charged Coupled Devices is to try to spill excess
> current into non-recording channels between the sensor rows, but in
> extreme situations, even the channels cannot flow the excessive amount
> away so it jumps to the next row or set of sensors.
> This is a design issue and there isn't a heck of a lot to be done if
> that is the cause. Different types of CCDs handle this issue with
> differing designs.
> 2) Using a glass carrier doesn't help this situation, because glass
> doesn't transmit light perfectly in straight columns. There is all sorts
> of internal reflection (bouncing between the surfaces and due to the
> density differences between air and glass surface, film and glass
> surface, etc.)
> If you are using a double sided glass carrier, you have the following
> interfaces taking place:
> Air/glass surface/glass interior/glass surface/air/film non-emulsion
> surface/film plastic base/film emulsion/air/glass surface/glass
> interior/glass surface/air, and that doesn't include any surface defects
> like scratches, surface residue on the glass or film, etc.
> That's quite a few places for diffraction, reflection, and general
> bouncing around of photons.
> If you can, I would try scanning without the glass carrier and see if
> that helps (I realize it adds the problem of the surface sagging causing
> focus issues), but it might tell you where the problem is coming from.
> If you do determine that the glass is adding a lot of this smearing, you
> might consider using a wet mount system, where a liquid is used (usually
> an oily substance) that the film is floated in between the glass
> surfaces. This liquid removes the diffraction differential between the
> air surfaces and the glass and film surfaces, which reduces the total
> number of surface for reflection and diffraction. It does demand careful
> use, to prevent dripping, air bubbles, picking up dust and dirt, and
> careful cleaning of the film and carrier afterward.
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