exposure calculation with paper negatives

Hello, all of you friendly folks:

I am new to this discussion, and I have enjoyed reading your posts and
looking at many of your websites. The pinhole world includes many very
talented and dedicated artists.

I recently re-kindled a long dormant interest in photography by
constructing several pinhole cameras. I read as many of the internet
instruction sites as I could digest, and went forth into the world to
make pictures. I used Guillermo Penate's suggestion of ASA 6 for RC
paper, and taped a copy of his reciprocity failure chart to my copy
paper box camera. Most of my attempts have turned out over-exposed. I
am using Ilford MG IV pearl paper. This morning I exposed a sheet in
bright, early-morning sunlight. My meter (set at ASA 6) said 1/4 sec
at f16. My aperture is .508 mm with 205 mm focal length, for f404. My
little cheat sheet says double the reading nine times, then apply
reciprocity factor. I exposed for 2 minutes (which does not include
any reciprocity allowance), and got a very dark negative - it will be
printable, but it will be a challenge for my rusty chops.

My camera is light-tight, and I am pretty sure of the accuracy of my
pinholes. Is the effective ASA of the paper higher than 6? I love the
few images that I have been able to print, but it is a struggle. I
would like to graduate to film, but I want to be more sure of my
exposures before I start burning up the expensive stuff.

Any suggestions would be appreciated.

Earl Johnson
Inver Grove Heights, MN
earlj@comcast.net

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Received on Tue Mar 16 19:08:36 2004