Exposure 4 created double exposure

[peter k.]

How does one figure the correct exposure for a double exposure.

As in you want to put one image on top of another. The first image would be the background... and the second image would be what wanted to be portrayed... the actual subject of the shot.
First Image: Say it was a bright day, using an ASA of 200, wanting the background to be all in focus, one could shoot f16 @ 125, for a normal shot.
Second Image: Close subject, in shade, with a narrow depth of field, say f8 @250.

Would the second shot cause the first shot to become overexposed?

 

[RobC]

1st and 2nd exposures are cumulative.

 

[peter k.]

1st and 2nd exposures are cumulative.

ok, that's what I thought, x

Check out this thought process on how I perceive what your saying ..
If you under exposed the first negative, it would be a denser then the final negative, until you add more exposure, with the second image.

Say you want the first image, when printed out, to look like the correct exposure, when the double exposure is completed.
So what would be approximately the correct way to perceive the first image.. setting?
Two stops closed? f32@125?
and keep the the second, f8 @ 250?

Info:First Image: Say it was a bright day, using an ASA of 200, wanting the background to be all in focus, one could shoot f16 @ 125, for a normal shot.
Second Image: Close subject, in shade, with a narrow depth of field, say f8 @250.

 

[RobC]

Can't answer your question becasue it really depends on how light the 1st image is and how light the 2nd image is. They will always merge together becasue the two exposures are cumalative.

But if first image is a very dark background and second image is also a very dark background but with a very well illuminated main subject, then the second exposure main subject will only blend into 1st exposure a tad. But if 1st exposure is a medium tone and not sufficiently dark then 2nd image will blend in a lot more unless you overexpose 2nd exposure.

So you are going to need to experiment with dark and mid tone backgrounds to see what the final effect will be becasue it is so dependant on cumulative result from two different lighting and exposure situations.

AND

If you are using colour film then you may well get some strange colour combinations.

 

[peter k.]

Makes sense... will give it a try... and no way about trying this in color

 

[Alan Gales]

Makes sense... will give it a try... and no way about trying this in color

If your subjects can easily be recreated like a still life or portrait then try it first with a 35mm camera. Take notes on what you did and if you get what you want then recreate it with large format. Double exposures can be hit or miss.

 

[Bill Burk]

RobC has it right, the exposures are cumulative. Theoretically you would divide the exposure required by the number of shots and set accordingly.

But... although you need only half the exposure per shot...

That only works "if" you have circumstances working in your favor. For example the camera on a tripod and the subject tries to stay still. (or if you or the subject don't move much between shots). Or if the two shots are average light. So in other words, if you set it up in a way that the shots will add up... then do some math and reduce exposure per shot accordingly.

Soon as you put in a dark background, then you have a chance to make individual shots that each requires regular exposure.

I have experience shooting double exposures where each received regular exposure and the result is "just fine".

Black and White Negative film can take a great deal of overexposure. So if I were deliberately planning double exposures, I would simply use the exposure for one shot, and take the next. After all, it works out fine when I do it accidentally.

 

[Vaughn]

Like Bill, I suggest taking both images at their normal exposures -- unless I wanted one image to dominate the other, in which case I would reduce the exposure of the less-dominate image by half.

 

[Alan Gales]

I've had the same experience as Bill shooting both images at their normal exposures. I messed around with double exposures with 35mm a long time ago. Sometimes I liked what I got and sometimes I didn't. It's fun though!

 

[Poisson Du Jour]

Double the baseline ISO of the film you are using. If you're using 50ISO film, go to EI100 or EI125. 200ISO to EI400 and so on. It's a bit more tricky and of a judgement call if using a camera set in 0.3 step exposures, as up to +/– 0.6 it can introduce overexposure -- a problem only when working with transparency film as opposed to B&W film with heaps more latitude (and this is what gets you over the line more often than with tpy film). Additional problems can develop if you shoot the first or second exposure in different lighting e.g. strong (point) light for the first or second, vs. soft (diffused) light for the other. I have found multiexposures with medium format are far easier and predictable (in conditions which don't in themselves add problems to exposures) than smaller formats e.g. 35mm.

 

[pdeeh]

Am I wildly off base by thinking that the first exposure will act as a "flashing" exposure and either alter the contrast of the second exposure or perhaps even mean that the required exposure is reduced for the second exposure?

(I realise this is rather more a theoretical question than a practical one and that for photographic purposes it wouldn't make a difference - even if I've actually got hold of the right end of the stick for a change)

 

[Vaughn]

Yes, you are.

 

[pdeeh]

Excellent.
Now explain why and I'll learn something

 

[RobC]

Excellent.
Now explain why and I'll learn something

Flashing means giving just enough exposure to use up the zero to threshold of exposure. When done on film it will give just the shadows a slight lift. Flashing is normally done using an even toned subject or diffusion filter. This is not what the OP is describing. Please read the OPs original post before making kneejerk assumptions. Touche

 

[Bill Burk]

pdeeh,

You might be wondering... "Will the flare from the first exposure improve the shadow rendition of the second exposure?"

To which I think the answer might be the obvious: The first exposure is very likely going to put a strongly exposed image in the shadows of the second exposure.

 

[nosmok]

I used to carry around an old Graflex RB slr, and shoot double exposures hand-held. I'd either shoot the 2nd pic on a dark first pic or use my hand to mask off alternate parts of the frame. It worked pretty well either way, so I don't think one needs to overthink it. There will be a learning curve so best to make some test shots.

 

[Vaughn]

Excellent.
Now explain why and I'll learn something

Actually, it does not really matter which exposure is first or last. As far as flashing, there might be a little of that happening in small areas of the image -- just where two deeply shadowed areas over-lap. Those areas might reinforce each other in a way that is similar to flashing.