filmscanners: Re: Emulsion flaws (was dust in SS4,

[Roger Smith <rsmith@unb.ca>]

At 9:20 AM -0400 9/23/01, Tom A. Trottier wrote:
>I find this all very puzzling. I'd suspect your water if it hadn't
>been "double distilled."

Hi Tom,
        Thanks for your interest, and suggestions. They are all good, 
but as you will see in the next line below, they don't apply to the 
present situation, but that's my fault.

        I have to retract part of my previous statement about the 
"bubbles" not appearing in undeveloped film.
        Both Art Entlich and I had trouble believing that bubbles (or 
whatever they are) could form, during developing, in the protective 
layer over the emulsion, so I had another look through the microscope 
at a piece of undeveloped Kodak Elite Chrome film. Using very careful 
lighting and focussing, I now see that the "bubbles" are indeed 
present in undeveloped film. They are just very hard to see against 
the very dense background. Sorry to be so misleading on this matter. 
It does make largely irrelevant any question of this phenomenon being 
caused by quirks in developing or drying the film.

        The question still remains - do these "bubbles" cause some of 
the "dirt spots" many of us see in the lighter areas of our scans. I 
put an Ektachrome 64 Tungsten slide, which contained a lot of white 
subject matter, under a dissecting microscope at 80x magnification. 
The bubbles were extremely visible and appeared similar in size to 
some of the "grain clumps" or dye clouds forming the image. If Tony 
Sleep and others are correct about the grainy appearance in scanned 
images being caused by aliasing effects between the scanner CCD 
(particularly in 2700 ppi scanners) and the "film grain" then it 
seems to me these highly visible "bubbles" should also have some 
similar effect.
        I'd like to know if they are visible in a 4000 ppi scanner, 
and if so what appearance they have. If someone with one of these 
wonderful machines would like to scan a few slides containing a lot 
of light or clear area, (which is the only place the bubbles would be 
easily visible), I would be interested to see the results.
        Whether or not they are visible in prints is another question.....

Regards,
Roger Smith