“As the light level decreases out of the reciprocity range, the increase in duration, and hence of total exposure, required to produce an equivalent response becomes higher than the formula states” (see Wikipedia entry).
Those of us coming from having shot a lot of digital, especially when you’re experience of low light photography is entirely with digital are going to get a bit of a shock at some point. Why didn’t this image work exactly as I wanted it to? Why isn’t there as much.. well.. image!
You’ll probably read things like “you don’t need to worry about it until you’re into really long exposures” or maybe you’ll start reading the manufacturers documents on the properties of the film and just go “whatever”.
Ilford Delta 3200 Professional is one of the films where you have to start caring about it pretty quickly. Basically, you need to overexpose once you start getting exposures greater than ~1second.
In decent light, handheld with a pretty quick exposure, things look great:
But whack things on a Tripod and have a bit of a longer exposure you’re going to start failing a bit. Even though I like this shot, I find that it’s just not quite got everything I would have liked to capture. Just exposing a bit more I think would have done it. I had to do too much in scanning and the GIMP…
So I learnt something with this roll, which is always good.
The worst part of reciprocity failure is that it’s so hard to accurately gauge.
I tend to shoot on rather slow slide film, and for anything longer than a couple of seconds have to bracket heavily, up to 4 stops over for very long exposures.
You probably have it worse on the slide film because of the narrower latitude you have (one advantage of print film :)
On the other side of the coin, transparency/slide film is not as grainy as negative/print film, so may be more tolerant in low light situations?
Although really fast slide film doesn’t really exist, so that will mean longer exposures. an issue with people in low light.