Low-light/night photography and reciprocity failure

I’ve got yet another reciprocity failure question to add to the forum. Or maybe it’s more of a question of application under low-light conditions.

When photographing just after the sun has gone down, I’ll take a meter reading, and adjust for reciprocity failure. Let’s say my metered reading says to expose for 2 minutes. After adjusting for R.F., using Portra 160, the new exposure time would be about 12 minutes. But, since conditions will have gotten even darker in the 12 minutes that pass while the shutter is open, is it necessary to further correct on the fly and lengthen the exposure even more? And what about the reversed situation before the sun rises, and conditions are getting brighter?

Am I trying to be overly precise? Or is this something to actually try to adjust for?

this situation is really tricky, and it's the same in film and digital photography. You do long exposure and light is decreasing so it make sense that you add more time. Once I shoot sunset long exposure with my digital camera with 10 stop ND and although I adjusted the time to counter the ND the image came out not as I like. It was 8 minutes exposure and light at sunset or sunrise change fast. The solution is to give from 20% to 40% more time or whatever extra time you feel. It would come with experimentation and practice. Problem is that you can't bracket cause after 12 or 15 min exposure that's it. it's totally new lighting condition so best is to try next day

AndyDDuncan said:

I’ve got yet another reciprocity failure question to add to the forum. Or maybe it’s more of a question of application under low-light conditions.

When photographing just after the sun has gone down, I’ll take a meter reading, and adjust for reciprocity failure. Let’s say my metered reading says to expose for 2 minutes. After adjusting for R.F., using Portra 160, the new exposure time would be about 12 minutes. But, since conditions will have gotten even darker in the 12 minutes that pass while the shutter is open, is it necessary to further correct on the fly and lengthen the exposure even more? And what about the reversed situation before the sun rises, and conditions are getting brighter?

Am I trying to be overly precise? Or is this something to actually try to adjust for?

Click to expand...

You are trying to get too much depth of field
If you open 2 stops, you end up with 30" and no RF problem. And you can bracket, and your entire picture is within the same light condition.
If you go down the road of RF, then you also have chromatic "failure", some star trails etc. and, in general, I think this unnecessary complication would probably work against the image you are trying to obtain, unless you have a specific reason for a 2' exposure. I would keep things easy.

Any way the point is theoretically interesting so if you try it let us know!

Thanks for the input so far!

To your point, Diapositivo, maximum depth of field is something I always try to achieve, so I’ve usually got the lens closed down fairly tight. I also aim for longer exposures, because I’m interested in showing the passage of time in a single image. I guess I should mention, I’m photographing landscape, where there might be a breeze moving grass or trees, or running water, or clouds moving in the sky. So, I actually don’t mind sitting around for 15+ minutes waiting for my film to expose.

Out of convenience, I went all digital about 8 years ago, but last month I got back in to film and bought a Fuji GSW690iii. I’ve put one roll through it, and, boy, am I rusty. Digital turned me into a pretty sloppy photographer! I know I’ve got at least one frame on that first roll that is out of focus and another that’s going to be underexposed...because I forgot to adjust for reciprocity failure! Back in my days of film photography, I mainly used a Kodak Eastman Century View No. 1 5x7, but only shot black and white, and did all my own developing in Pyro. I actually loved that there was/is such a thing as reciprocity failure, because that meant my exposures would be even longer! But then was sad about the fact that R.F. doesn’t exist in digital...But with black and white film, there are no color shifts to worry about as there are with color film, so that’s never been an issue for me. I didn’t even know that is was something to worry about. I guess it is an issue now...

Back then, this topic of losing light as the exposure goes on and the possibility of needing to correct for it never really struck me for whatever reason. Hence, the question. It really is a fun puzzle to work out!

If you double your exposure to 24 minutes, that's only one stop over what you had expected and factoring in further R.F. would mean that you're really only over by less than a stop. Seems like it's not that risky in the long run.

True, rwreich. I've found it is a bit hard to overexpose in low light conditions.