In article <4a6f56$6kb@juha.fi>, teemu.virtanen@ytv.fi says...
>I've heard a rumour that normal photographic paper can be used as a
>negative especially in large format cameras and/or pinholes. Could
>someone please help me and explain how that happens? Film(!?) speed of
>paper?, Developing process? etc. I need pictures that are positives not
>negatives.

This works very well, is cheap, and gives (relatively) instant feedback.
I learned printing (by doing it) in the San Francisco city (public)
darkroom in the '60's (uh-huh!). One thing I was fond of doing was
putting photo paper in a pinhole camera (well, I cheated, and taped
a simple magnifying glass lens behind the pinhole...) (the camera had a
curved "film plane" for super wide-angle photos), run outside, expose
the paper, run inside to the darkroom and develop it (and often run
back outside with the wet under-fixed [it turns such pretty colors!]
paper to compare the photo with the scene photographed). For starting,
try to use a grade one RC paper, rated about 4 ASA (start with the
assumption that the pinhole is f256 - change the ratings to values that
work for you with experience [paper is CHEAP!]). The dry paper can be contact printed for the positive, though paper negatives shot in
a view camera are EXTREMELY sharp looking, and have an appealing
aesthetic of their own (trademarks, like those on on the back of Kodak paper, do not seem to be a problem). BTW, this is a good quick way to get decent B & W positives from color slides: Print the slide (using
an enlarger) on grade one RC paper, then contact the paper negative
on grade one for the final print. Color sensitivity will cause some
problems in tonal relationships compared with the original, but the
results are often excellent for emergency use.
Hope this helps.