filmscanners: Re: Emulsion flaws

[Roger Smith <rsmith@unb.ca>]

At 8:37 PM -0400 9/23/01, Austin Franklin wrote:
>I'm curious.  Has anyone ever heard that this is a "problem" previously?  I
>mean, film has been around for decades...as well as exceptional cameras,
>very good enlargers, and enlarging lenses...and people (including my self)
>have made some very large prints....but never have I heard anyone, out of
>hundreds of high end professionals and amateur photographers I know, ever
>mention "emulsion bubbles" as being a problem...
>
>I've also not heard any of the high end scanner people I know (who use drum
>scanners, Leafscans and Imacons) ever mention this issue either...

        Yeah, I know. I'm curious, too. I made Cibachrome prints for 
25 years on a Durst using Schneider lenses and never saw any trace of 
them either. In fact, many of the older slides I'm seeing bubbles in 
now were the ones I printed. I think it is a matter of focus - when 
the emulsion is in focus, the bubbles are almost invisible.
        Curiously, one slide in particular (Ektachrome 64 from 1979), 
which I printed many times on Cibachrome and scanned using a Canon 
FS2710, showed no particular flaws. When I got a new Minolta Scan 
Dual II, I was shocked to see hundreds of specks and small lines in 
the sky area. When I examined it under a dissecting microscope using 
oblique light, all the marks showed up clearly. Most of them were in 
the base side of the film rather than the emulsion side. This has 
nothing to do with the present "bubble" discussion except to point 
out that some things invisible to conventional enlargers do show up 
on some scanners.
        It also does nothing to explain why high-end scanners and 
huge enlargements don't show the bubbles, either. I expect someone 
out there will have an answer.
        I started my investigation in response to a list member who 
was getting hundreds of tiny spots in Polaroid SS4000 scans from 
slides that seemed dust-free. I still think the "bubbles" are too 
small to show up as discrete spots, but they may have an effect on 
the "grain-aliasing" phenomenon.

Regards,
Roger Smith