Re: [APML] Black Negs a new developement

[Robert Reeves <reeves10@swbell.net>]

> thick enough to ruin the film.  I am in the far west suburbs of Chicago,
on
> each night I am sure we were in the 60% humidity range.  Is that too high
> without a purge?

Thats high enough humidity to NEED a purge, but not so much that it will
turn the negative completely black.  Before I fabricated the purge system
for my Schmidt camera, half hour Tech Pan exposures often hit higher
humidity than that.  The film was open to the air inside the large volume of
the Schmidt camera.  It badly reduced image contrast, to the point of
rendering the exposure useless, but didn't turn TP black.  It was a very
dark gray but the image was still visible.

Robert Reeves                      reeves10@swbell.net
520 Rittiman Rd.                   www.robertreeves.com
San Antonio, Texas 78209    210-828-9036
USA                                     29.484  98.440  200 meters


--  APML Archives at <http://astro.umsystem.edu/apml/>  ---
             Unsubscribe at <majordomo@seds.org>