What's the lighting rule for double exposures?

[Markster]

Say you want to hypothetically double expose a negative, to super impose 2 images on the same film.

What's the rule with light on the film? You use 1/2 of the light setting for each exposure? Or is it more like 2/3? I would imagine that exposing both at full light would blow out the end product a bit.


Just curious. Probably a dumb question, but it came to mind today.

 

[Neanderman]

My photo professor, who did a lot of multiple exposure work, said to just make two 'normal' exposures. All the ones I ever made using that rule were fine.

Ed

 

[Jim Noel]

If each exposure is given one-half the indicated exposure, the negative density in the overlapping areas will be"normal"

 

[2F/2F]

It depends. You can stack two normal exposures to end up with a neg that is one stop overexposed overall, but that can easily be printed. You can also cut a stop from each shot when shooting to end up with a neg that is overall correctly exposed. However, if you do this, each image will be one stop underexposed, with all the effects that come from this. For instance, you may lose some contrast and shadow texture and detail. Then again, sometimes areas of pitch black are what allow double exposures to really work well, as you can stack bright elements of the second exposure onto dark areas of the first and get less clutter. It depends on what you are doing and what you want.

 

[RalphLambrecht]

My photo professor, who did a lot of multiple exposure work, said to just make two 'normal' exposures. ...

For negative film, I agree with your professor. With double exposures, the 1/2+1/2 theory can lead to underexposure in some image areas. This is a far bigger problem than overexposure for negative film. Therefore, the overexposure, potentially caused by two normal exposures, is a much smaller risk, and probably turns out to be no risk at all but a benefit (improved shadow detail)!

 

[Mike Wilde]

It also depends on the desired effect. It may be advisable to cut exposure back on the second 'ghosted image', and expose the primary image as normal, if you do not want a 50/50 double exposure.

 

[picker77]

It also depends on the desired effect. It may be advisable to cut exposure back on the second 'ghosted image', and expose the primary image as normal, if you do not want a 50/50 double exposure.

Not sure if any rule applies here, this triple exposure was made on a Bronica SQ-Am in aperture priority mode. I was new to the camera, and was screwing around with the multiple exposure lever, so I didn't note the settings the camera chose for the three shots, but the results were interesting enough that I scanned the negative after development. Almost gave a shortened telephoto-like effect, as if using a long lens in fog, but it was not foggy that day, lol.

 

[RalphLambrecht]

That's actually a very interesting image. I like it!

 

[moki]

As a rule of thumb, stopping down one step (or halving the time) for 2 exposures to 1 frame is good enough. With negative film, it will always give you a decent exposure, but some combination of exposures may need less compensation. Of course, you can also underexpose one by 1.5 stops and the other by 0.5, if you want one picture to be more dominant. This is not mathematically precise and applicable in all situations, but good enough, even for color slide film. For multiple exposures (three or more), half the number of exposures is the number of steps to stop down... 3 exposures is 1.5 stops, 4 exposures is 2 stops and so on.

 

[RalphLambrecht]

As a rule of thumb, stopping down one step (or halving the time) for 2 exposures to 1 frame is good enough. With negative film, it will always give you a decent exposure, but some combination of exposures may need less compensation. ...

I doubt this will lead to anything but underexposure.

 

[hirokun]

I mostly shoot slides & b/w negs. But as for double/multiple exposures I've only used slides so far. I always went with 1/2 + 1/2 or more generally speaking: 1/n + 1/n + ... + 1/n.

But that depends on the scene. Sometimes I want one exposure to be more "dominant" than the other one, so I do 1/3 + 2/3 or even 1/4 + 3/4...

Or imagine overlapping two scenes, that are horizontally/vertically split... If, say, on the first exposure you have a bright top and a dark bottom, but on the second exposure you have the opposite situation (dark top, bright bottom), then I'd just do 1+1 or to be safer 2/3 + 2/3...