Marco B
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At 40mins surely recipricity failure is a far bigger issue than ISO? Get some film data sheets - I'd have a look at using acros.
Thanks all for the suggestions!
The reason I was looking for something like ISO 1600 is a kind of madmen's project: shooting night time pinholes of illuminated buildings with an ultrawide 4x5 pinhole camera...
I have had some preliminary results with about 40 min exposure that showed some promise, but the negs are thin. I did not really push develop though, and did not pre-flash the film. I will give it a try with HP5 and see what I can come up with... and possibly see if I can buy some of that Rollei stuff with the High Speed developer.
At 40mins surely reciprocity failure is a far bigger issue than ISO? Get some film data sheets - I'd have a look at using acros.
Wowzers!
>SNIP
Interesting, but no help. However, I do recall reading somewhere about how you can push film by exposing the underexposed, but normally developed film, in an airtight chamber, to the fumes of hydrogen peroxide, heated to a temperature of about 100F. I have never seen any info online about this procedure; I will search my printed records at home this weekend. If I can find the original article (from about 1973, I think), I'll drop you a PM.
SNIP<
you may find that the reciprocity of the faster films make them slower than 100 speed films when used at long exposures.
I think it is an idea to find the film that suffer the least from recipocity failure
Thanks Eddie. You may be right... I must say I was already slightly surprised looking at the reciprocity table of Ralph. I lists LESS time for TMax 100 compared to 400 for long exposures. E.g. measured 15 min translates to 40 min for 100 and 1h10min for 400 ISO TMax.
It was confusing to me, until you now explained it... learned something valuable new here.
Does anyone actually have a technical explanation for this phenomenon, slow films being FASTER than fast films at long (reciprocity failure) times? :confused:
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