Re: pinhole exposures

----- Original Message -----
From: <PinholeRenner@netscape.net>

> > all the above . usualy asa 100

Undoubtedly, your pinhole exposures would fall into the nightmares of
reciprocity failure. Each film (emulsion type and speed combined) will need
different corrections (Tmax100 would need different corrections that Tmax400
and different from Delta100, for instance). Knowing the speed you use is
not enough to help you with reciprocity corrections, we need to know the
emulsion(s) you use.

>> I saw a web site that you could put the f-stop & it would give you the
correct speed .you take a reading with your slr or light meter & then adjust
it to match your pinhole camera. I have lost the url for that site. anyone
familiar with that site ?

Gregg posted Mr.Pinhole's calculator page's URL in another post. That
calculator is helpful to translate your metered exposure to your pinhole
camera exposure, but do not include reciprocity corrections (it says so at
the foot of the page). You can print the resulting chart for each of your
pinhole cameras f/stop and carry it with you.

I believe it helps to know how to translate exposures in case you
lose/forget the charts. What you do is to find how many stops of difference
there are between (let's say( f/16 and your pinhole camera. If your pinhole
camera is f/212 (i.e.) I would approximate that to f/256 and count the
f/stops separating it from f/16. They are: f/22 (1 stop), f/32 (2 stops),
f/45 (3), f/64, f/90, f/128, f/180, f/256 (8 stops). There are 8 stops
separation between f/16 and f/256, that means that if you take a meter
reading based on f/16, you'd have to DOUBLE the given exposure time 8 times
in order to have an equivalent exposure for your pinhole camera. I.E., you
take a meter reading and get f/16 @ 1/250 secs, you then double 1/250 eight
times, like this: 1/125 (1 doubling), 1/60 (2 doublings), 1/30 (3), 1/15,
1/8, 1/4, 1/2, 1 second (1 doublings), therefore the equivalent exposure for
f/16 @ 1/250 seconds is f/256 @ 1 second. See, no math involved just
arithmetic (there are other "easier" methods but involve exponential, which
do qualify as math).

Guillermo
Received on Sun Jun 24 13:26:31 2001