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Re: filmscanners: Emulsion flaws (was dust in SS4000)



Roger, it would also be interesting if you exposed two identical rolls of film, sent one to a good lab for processing, and then processed the other yourself.  If the "bubbles" appear on both rolls, then they would be related to the film or the processing chemicals.  If they only appear on film that you process, then you would want to vary your processing technique until you found a way to make the bubbles go away.  I know that water, or a water based developing chemical, that is saturated with air and gases and has its temperature raised by even a few degrees will readily form small bubbles on anything submerged in it, including film, as the excess gas tries to escape the liquid.  That might account for the fact that you have an old roll of Kodachrome with "bubbles."  This is all speculation on my part.  The "dirt" that I once saw on several rolls of transparency film was to small to see with the na! ked eye.  When scanned, it looked like small black spots.  I never looked at them with a microscope.  They were easy to remove with the clone tool without doing any damage to the image, but it was somewhat tedious.  I haven't had that problem since, but suspect contaminated processing chemicals.  I think that most of the problems people have with dust involve pieces large enough to see with the naked eye.  They can easily be removed with a brush.  But dirt and "bubbles" embedded in the film are not common and there's really no excuse for them.

For what it's worth, I sometimes go to the effort of boiling water for a few minutes if I want to use it to mix darkroom chemicals that I don't intend to use up right away. Boiling removes most of the air, oxygen, and gases from the water.  I let it cool in air tight bottles in the refrigerator before using it to mix chemicals.  You might try that if you think the bubbles on your film are due to gases precipitating onto the film during processing.  Like I said, I'm only speculating.  But if the bubbles are making it difficult to scan the film, I'd sure look for a solution to the problem rather than rely on something like ICE to fix a problem you shouldn't have in the first place.

In a message dated 9/21/2001 8:52:25 PM Pacific Daylight Time, artistic@ampsc.com writes:


How very interesting!

I am now more sure of my theory.  Either these bubbles occur during
manufacturing or processing, and are, I suspect, either introduced in
the base plastic or as the coatings are layered onto the film, or, the
processing creates some gas which doesn't fully migrate out of the
emulsion during washing and drying.

Art

Roger Smith wrote:
>
> Martin and others:
>         This is another Roger (not Miller), but I have been following
> the "Dust" thread with interest.
>         I have often noticed tiny spots on my scans (particularly
> since I got a Minolta Scan Dual II, which shows the spots much more
> than my previous Canon FS2710).
>         I stuck a Kodak Ektachrome 64T slide (that I developed this
> morning) under my microscope and cranked up the magnification to
> 400x. The enclosed Nikon Coolpix 995 image taken through the
> microscope shows what I saw. This is an area of the slide which is
> almost transparent - the orange area at the bottom shows the film
> grain. The bubble-like flaws are in a different plane from the grain,
> on the outside layer of the emulsion. I can tell this by where I have
> to focus the microscope to see them.
>         I developed the film myself, using double distilled water for
> the final rinse. I must admit this is one of the worst examples of
> these bubbles I have seen, but they do show up on most of my slides,
> on many different types of film. I thought it might be the result of
> a processing error, but then I saw the same bubbles on a Kodachrome
> 64 slide from 1975.
>         Any ideas?
>
> Regards,
> Roger Smith




 




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