Reciprocity failure during long exposures

Messiah Khan

Messiah Khan

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Alasdair Fowler
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I sort of know what it is, but could someone please explain to me why it occurs, and how I would work around it? Im planning on doing some very long exposures (Up to an hour or more, and I see reciprocity failure being a problem)
 
You've probably done this already MK ... :suspect: ... but at least it will save following viewers the trouble ... :D


Reciprocity Failure according to the Gospel of Wilkie ... !



editsmily.gif
... Good news for digital camera users ...

... Reciprocity failure is not a problem with digital cameras, however noise can be. ...

From HERE ... !


HTH ... :D



At least I've learned something new today ... ;)









:p
 
Hehe, cheers Ven. I'll admit I hadn't actually read that. One bit I can't quite follow though;

Best exposure time in seconds = 2.5 (Metered exposure time in seconds) 1.5

which can be used as a rule of thumb for very low light exposures of standard color print film, metered for a second or more. A metered one second really required 2.5 to expose the film accurately, and a metered 60 seconds really required nearly 20 minutes.
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My math skills arn't the best, so could someone explain that formula a bit. And thanks for the ninja edit Ven, as that was going to be my next question; Digital. Ok, so presuming I don't have reciprocity failure, but noise is a problem. Is there anyway to overcome this or at least minimise it other than shooting at iso100?
 
Messiah Khan said:
Hehe, cheers Ven. Ok, so presuming I don't have reciprocity failure, but noise is a problem. Is there anyway to overcome this or at least minimise it other than shooting at iso100?
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:lol: ... no worries MK ... :thumbs:


Get a decent Noise Reduction programme ... :shrug: ... ;)


Surely you don't need to worry about the formulae ... being digitised 'n all ... :D ... I know a cop out but what you gonna do ... :naughty:





:p
 
Reciprocity failure is the breakdown of the reciprocal rule running through the whole of photographic exposure principle, i.e. a halving of aperture, leads to a doubling of shutter speed and vice versa. Similarly, a doubling of ISO setting results in a halving of exposure time and vice versa.

It happens because of the nature of the sensitivity of film, and varies greatly from one film to another. It can also happen at very fast exposure times as well as long ones. For this reason going back 20 years or so, you had to reckon on figuring reciprocity failure into your calculations with any exposure much longer than one second, and you didn't see shutter speeds on cameras in excess 0f 1/1000 or 1/2000 of a second. As film improved, reciprocity failure became less of an issue and shutter speeds increased, although the reciprocity issue was still there - just the boundaries pushed a little wider.

Film manufacturers publish details of recommended increases in exposure time to account for reciprocity failure. Sometimes there are brief details on the paper slip packed with the film, but these days a web search should turn up reciprocity data for your favourite film stock.

The good news as far as I've been able to ascertain is that reciprocity failure is no longer any serious issue with digital photography, and is as dead as a Norwegian Blue.
 
Joe T said:
Does the D40x have Nikon's long exposure noise reduction function?
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Good point Joe. That system works by duplicating the image and comparing the two. Because noise is entirely random the system removes any artifacts not common to both images. I had this system on a Nikon compact and it worked really well apart from totally bolloxing up the definition in the process.:D
 
It should do, and it's what you'll want to use.

As well as noise digital cameras pick up a lot of hot pixels in very long exposures. The long exposure noise reduction takes a second exposure of the same length (or thereabouts) with the mirror down, then subtracts that exposure from the first... Reducing the appearance of hot pixels.

The other fun problem is battery power. The longest I've managed with my D200 is 3 hours (~5 hours with long exposure NR), and that's with two fully charged batteries. You should be fine for an hour or so, though.

edit : wrong kind of thing, Cedric. the long exposure NR feature on Nikon's dSLR's will only reduce (or eliminate if they aren't too prevalent) hot pixels & heat related issues (purple haze near the edges of the frame, different between SLR's and only an issue with really long stuff). It won't make a jot of difference to actual traditional noise.
 
Joe T said:
Does the D40x have Nikon's long exposure noise reduction function?
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Aye that it does. Wonder how effective it is over extended exposures. The type of shots im after are like the work of one of my favourite photographers; David Burdeny http://www.davidburdeny.com/ I know he uses MF film cameras, but I wantto see what I can do with my current equipment.:)
 
Some really excellent stuff on his site MK ... :clap: ... not seen this before ... ;)









:p
 
CT said:
The good news as far as I've been able to ascertain is that reciprocity failure is no longer any serious issue with digital photography, and is as dead as a Norwegian Blue.
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:agree:

And I also wanted to post CT's comment again, because apart from being true, I just liked the way it scanned...'dead as a Norwegian Blue', or possibly just sleeping. :D
 
Shuffled off this mortal coil mate - pining for the fjiords. :D
 
Hoodi said:
edit : wrong kind of thing, Cedric. the long exposure NR feature on Nikon's dSLR's will only reduce (or eliminate if they aren't too prevalent) hot pixels & heat related issues (purple haze near the edges of the frame, different between SLR's and only an issue with really long stuff). It won't make a jot of difference to actual traditional noise.
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Ah.. I'm obliged. Different thing then. I think Nikon called the system on the compact 'Clear Image' or something similar.
 
Hoodi said:
It should do, and it's what you'll want to use.

As well as noise digital cameras pick up a lot of hot pixels in very long exposures. The long exposure noise reduction takes a second exposure of the same length (or thereabouts) with the mirror down, then subtracts that exposure from the first... Reducing the appearance of hot pixels.

The other fun problem is battery power. The longest I've managed with my D200 is 3 hours (~5 hours with long exposure NR), and that's with two fully charged batteries. You should be fine for an hour or so, though.

edit : wrong kind of thing, Cedric. the long exposure NR feature on Nikon's dSLR's will only reduce (or eliminate if they aren't too prevalent) hot pixels & heat related issues (purple haze near the edges of the frame, different between SLR's and only an issue with really long stuff). It won't make a jot of difference to actual traditional noise.
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Cheers Hoodi, that explains it well. I had considered the battery issue so i'll see how I get on. For normal shooting though I am very impressed with the battery life on this camera.

CT said:
Shuffled off this mortal coil mate - pining for the fjiords. :D
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I lived in Norway for over 10 years. Shame I wasn't in to photography then.
 
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