[Fwd: Paper Negative Mystery Follow-Up]

The message below seems to have gotten lost during the technical
difficulties, so I will post it again:

> Thanks to all of you who offered suggestions as to the cause of the
> overly dense and flat negatives that my pinhole camera produced in
> Alaska.
>
> The camera was leak checked and otherwise tested after the trip. The
> D76 was mixed fresh and has worked fine on negatives before and after
> the problem ones. The unused RC paper that I brought back has been used
> for both negatives and positives without any problem. So it looks like
> whatever happened, happened in the camera.
>
> As some of you mentioned, the problem may have been caused by excess
> blue and UV light around the water and in the higher latitudes of Alaska
> in general. The orthochromatic emulsions of B&W paper are sensitive to
> UV all the way down to about 200nm, and without any glass to attenuate
> it, the entire UV spectrum came streaming through that pinhole.
> (Separately, I recently heard someone mention that the ozone layer over
> Alaska has thinned, allowing more UV to reach the ground, but I
> would be a little surprised if the difference could be detected by a
> common photo emulsion.)
>
> I have been experimenting with some UV and yellow filters, and would
> like to hear of any filter and B&W paper combinations that others of you
> may
> have found useful.
>
> Thanks again,
> Bob
Received on Sun Oct 1 18:49:00 2000