RE: exposure calculation with paper negatives

Hello Earl,

When working with my students on their new cameras I check the "charts" then
I look at the results and apply my "gut" feeling. In 29 years of teaching
pinhole it has worked most of the time.

If they get a very dark exposure and a good image I suggest they bracket
their shots. Too dark, cut exposure time in half, but you must shoot under
the same conditions. They have the advantage of walking out of my classroom
door and right back to the darkroom. If the results are better but still
too dark the reduce time by 1/4. So my guess would be shoot again at 1
minute, if too dark move to 45 sec. Usually within 3 shots we have a usable
negative. I should mention I am a shoot by the seat of the pants kind of
pinholer. However the info from Guillermo, Guy, and many, many others have
taught me much about having better control. That is what is so neat about
this list.

I have also had my students who might be having problems with exposures and
shortages of materials cut photo paper into 1"x5" strips and tape them in
the center of the back of the camera and use them like a test strip.
It's all an adventure but what an adventure when you get those special
images!
Good Luck and hang in there!
Take Care,
Chuck Flagg

-----Original Message-----
From: owner-pinhole-discussion@spitbite.org
[mailto:owner-pinhole-discussion@spitbite.org]On Behalf Of Earl and
Patty Johnson
Sent: Tuesday, March 16, 2004 9:08 PM
To: pinhole-discussion@spitbite.org
Subject: [pinhole-discussion] 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 20:45:18 2004