Reciprocity failure and the handheld meter

[sparx]

Background first. Camera is Olympus OM40, max shutter speed (apart from bulb) 1 sec, so for longer exposures have to rely on my minolta flash IV handheld meter and a cable release. Just aquired some neutral density filters and want to take long exposure pics of the sea of between 1 & 5 minutes or so.

Question now. Do hand held light meters take reciprocity failure into account over longer exposures? I will be using Ilford FP4, possibly pulled slightly, as well as my ND filters and usually for me, a red filter. Any hints & tips would be greatly appreciated.

 

[Helen B]

No meter that I know of takes reciprocity failure into consideration. Different films have widely different reciprocity characteristics. Ilford's website has reciprocity data on FP4+ in the film data pdf, but I'd recommend doing your own tests to get the exposure/development balance right for the look you want. Reciprocity failure hits the shadows more than the highlights (as you probably know) so compensation development may be required - depends what you want.

Some slow films become effectively faster than 'fast' film when long exposures are used, because of their superior reciprocity characteristics. It's those lonely-heart silver atoms pining away, waiting for a mate so they can survive an hour instead of a fraction of a second.

I very much like Tom Cooper's pictures of the sea at night. There were made with exposures of a few hours.

Best,
Helen

 

[John McCallum]

.... It's those lonely-heart silver atoms pining away, waiting for a mate so they can survive an hour instead of a fraction of a second.

He he - beeuudifool.

I haven't seen any meters that take reciprocity failure into account either, because it is the individual films' makeup that dictates its performance during conditions of reciprocity failure. I tend to use FP4+ for the same situations that you are considering and found that using the exposure graph in pdf specs file for the film to account for RF works fine (in my experience up to 6-7 mins so far).
If you wish to allow for the effective change in contrast due to RF, Helen's suggestion of changing the development specs I think, is very good. Would take a bit of experimentation.
definately take a look at the FP4+ spec sheet to start with - it's actually quite easy.
regards, John.

 

[Ian Grant]

Why not try TMX in very low light levels its wonderful and hardly suffers from reciprocity failure at all and the negs are excellent tonally.

Must try these hours long exposures, at night in the landscape, but I don't own a watch and it was bad enough with 4mins @ f45 10days ago. But then give or take the odd 1/4hr will make no apparent differance. on a 2 or 3 hour exposure

 

[Graeme Hird]

Ian - go and buy a cheap watch from a drug store and keep in with your camera. $10 won't break the bank, will it?

As others have said, you'll need to allow for reciprocity failure on the basis of your film. Kodak has a few starting points for exposure times in their fact sheets. Try bracketing and make plenty of notes.

 

[sparx]

Just so i know i've got my head around this. I take a reading on my meter and it gives me a reading of, say 30 seconds. According to the Ilford data pdf my actual exposure should be just over 150 seconds. Am i in the ballpark and playing the right game?

 

[David A. Goldfarb]

That's right. First figure the basic exposure, then add filter factors, then any magnification/bellows factor (only an issue in 35mm for macro), and reciprocity last. I usually adjust the ISO dial on my meter to include filters and magnification factor, and calculate reciprocity manually.

 

[sparx]

Cheers for that everyone. Now all i have to do is go out and knacker some film.