Re: exposure calculation with paper negatives

I use the Mr pinhole exposure calculator.

See
http://www.mrpinhole.com/exposure.php

for your aperature

http://www.mrpinhole.com/cgi-bin/exposure.pl?Fstop=404

I print these out (usually reduce them) and tape them to the camera.

Try not correcting for reciprocity failure. Reciprocity failure is
specific to each film/paper type.

If you have the time, try photographing the same scene lighting conditions
with different exposures to determine an effective asa for your
camera/paper/developer empirically (educated guess/trial&error)

Gord

On Tue, 16 Mar 2004, Earl and Patty Johnson wrote:

> 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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---------------------------------------------------------
Gordon J. Holtslander Dept. of Biology
holtsg@duke.usask.ca 112 Science Place
http://duke.usask.ca/~holtsg University of Saskatchewan
Tel (306) 966-4433 Saskatoon, Saskatchewan
Fax (306) 966-4461 Canada S7N 5E2
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Received on Tue Mar 16 20:08:45 2004