Marcelo Mammana pinhole-discussion@p at ???????
Thu Mar 13 10:12:43 2003
>Here is my problem:
>I use Agfa Multicontrast Premium,
>The manufacturers chart, for when using the paper
>under the enlarger light, says that the paper has an
>ASA of 400p ("p" meaning paper?) when is used without
>filters, ASA160p when using contrast filters from 00
>to 3.5, and ASA80p, when using with filters from 4 up.
>Now, when I use the first camera, I get the best
>exposures when calculate them as if the paper is
>ASA64, but this is variable depending on the day
>(always measuring something close to a medium gray).
>For the second camera (a plastic 35mm film canister),
>best ASA is 125.
>In many Internet sources I've found that some people
>uses ASA 6 for paper and a very simple chart for
>reciprocity (1'', 10'' and 100'', corrected opening up
>1,2 or 3 stops), but this definitely makes grossy
>underexposed photos in my cameras.
If I understand correctly, you are saying that when you use ISO-6 you get
UNDEREXPOSED images and when you use higher rating ISO-64 or ISO-125 your
exposures are OK. That does not make sense.
BTW, collective experience tells me the "film speed" of B&W paper is just
about 1/100 the ISO "P" of the unfiltered paper, in the case of Ilford MGIV
with ISO-P=500, its speed would be ISO-5 or the more commonly used ISO-6, so
I'd expect the "film speed" of the Agfa multicontrast premium to be ISO-4.
IF in fact it is as fast as you say it is, it'd be the best paper to use for
pinhole purposes.
>2-Can, the same paper behave different just because
>the focal lenght differs
No.
Guillermo
