Re: Polaroid exposures

Bill,
        Here is a brief analysis I've done: Assuming bright open sky
conditions, shooting snowy scenes call for about +2 stops from whatever the
meter indicates for the snow. Using sunny/16, your exposure should be f/16
@ 1/25 secs. There are about 10 stops separating f/16 from f/500, therefore
for your camera, the uncorrected exposure time should be around 40 secs
(2^10 * 1/25). According to Ilford HP5 reciprocity correction, 40 sec
exposure should become 200 secs exposure. But according to Polaroid.com, an
exposure of 40 secs needs a correction of -2.7 f/stops for 804 film.
reciprocity corrections in f/stops do not equate exactly to corrections of
doublings of exposure time, but assuming they do, 40 secs should become
around 260 secs (2^2.7 * 40). BTW, it is not a good idea to use
reciprocity corrections charts for one film and apply them to a totally
different film/technology/manufacturer.

Could you tell us what's your metered or estimated uncorrected exposure time
and actual exposure times you have used?

Guillermo

----- Original Message -----
From: "The Painted Horse" <paintedhorse@in-tch.com>
>
> I could use some help here. We just got a wonderful spring time
> snowfall yesterday (10") and it got me out and about with my 8x10
> pinhole camera (due to the extra light reflection of the snow). I tried
> using Polaroid type 804 ASA 100 (first time using this film) and I can't
> seem to get the exposures correct. The prints keep coming out real
> light. Now, I could keep adjusting the time exposures but it is
> expensive film and I really don't want to use the whole box of film as
> testing material (that is, if I can help it).
> The camera is a normal focal length (13 inches) Leonardo 8x10 and the
> pinhole is F 500. Anyone out there do 8x10 pinhole Polaroids? For some
> reason the time charts I use for Ilford HP5 aren't working. And yes, I
> calculate for the difference in the film speeds. Any help would be
> appreciated.
Received on Wed Apr 4 14:40:27 2001