Exposure settings for multiple exposures

[seany65]

Hello all. I'd like to ask about exposure settings for mutlipe exposures.

I'm aware that if I want to do 2 exposures on 1 frame, I look at the exposure the meter suggests and change either shutter speed or aperture to the next one that gives less light to the film, eg. 1 shot at 1/125 @ f8 becomes either 2 shots at 1/250 @ f8 OR 1/125 @ f11.

But what I'd like to know is, if I want to do 3 shots on one frame would I do 3 shots at 1/500 @ f8 OR 1/125 @f16, if the meter gave 1/125 @f8?

I suppose this question could be extended for 4 or 5 shots on one frame.

Any help would be much appreciated.

 

[Huss]

3 shots = 1/3 of exposure per shot
4 shots = 1/4 of exposure per shot

etc etc

If you are using colour negative film (C41) don't worry too much about over exposing.

 

[seany65]

Thanks Huss. I did think that, but with each smaller aperture or faster speed giving 1/2 the exposure of the wider/slower speed, then the next smaller aperture or slower speed giving 1/2 of that, I've been trying to get my rather feeble brain around the whole 'how to get 1/3 of the exposure out of '1/2 of the exposure, then half again' thing.

 

[Ranchu]

I think you have to find it by times. Normal exposure is 1/30th, so three exposures of 1/90th. 1/30 to 1/60 is one stop, 1/60 to 1/90 is 1/2 stop, so 1/30 to 1/90 = -1 1/2 stops.

 

[seany65]

Sorry for the late reply, Ranchu, I've only just seen your post.

Unforutnately, the camera I'll be doing this with the most will be a gevaert gevabox which only has one speed, which 'could' be 1/30 (as I've seen that speed mentioned by others) or 'about 1/50' as it mentions in the manual, but the one in the manual has the two flash contacts on the bottom and my camera doesn't.

The other camera I could do M.E.'s with is a ricoh 500gx which has full-step speeds. On the other hand it does seem to have 'stepless' apertures.

 

[Roger Hicks]

If you're shooting neg film, just guess as best you can and err on the side of overexposure. Which, come to think of it, Gevaboxes are predicated upon. You are looking for more precision than exists: a stop or two or even three over is unlikely to matter.

Cheers,

R.

 

[Dwig]

You should also consider how the two, or more, images are going to overlap. If the highlight areas in one shot are going to overlap deep shadows in the other, then very little exposure compensation, if any, would be needed.

 

[Ranchu]

Sorry for the late reply, Ranchu, I've only just seen your post.

Unforutnately, the camera I'll be doing this with the most will be a gevaert gevabox which only has one speed, which 'could' be 1/30 (as I've seen that speed mentioned by others) or 'about 1/50' as it mentions in the manual, but the one in the manual has the two flash contacts on the bottom and my camera doesn't.

The other camera I could do M.E.'s with is a ricoh 500gx which has full-step speeds. On the other hand it does seem to have 'stepless' apertures.

That was just to figure out how many less stops for each of the three exposures. I was saying you have to use speed to figure it out rather than trying to figure it out using apertures. You could use the aperture to actually get the 1 1/2 stops when you shoot it, now that you know theoretically how much you need.

 

[Rob-F]

I think maybe you could set the exposure to a film speed 2/3 stop faster than normal. So if using ISO 100 film, maybe set the film speed dial to ISO 160 for the three shots.

 

[seany65]

Thanks to all for the further replies and ideas.

@Dwig, One of the reasons I'm thinking about Multiple Exposures is to build up the exposure to say, F5.6 or F4 with my gevabox (which only goes up to F8), if my lightmeter only gives me the option of those wider apertures. As far as I can remember from reading about it years ago this is a reasonable method of doing so.

I'm generally not after the 'traditional' M.E. stuff, which combines 2 or more images of different things, although I do think I may take several pics of people in the same scene so it looks like there's twins or triplets etc. just to add a bit of 'oddness' to the pics.

Using M.E. would be a supplemental idea to using ND filters to widen the possible range of exposures I can use with the gevabox.

 

[Dwig]

Thanks to all for the further replies and ideas.

@Dwig, One of the reasons I'm thinking about Multiple Exposures is to build up the exposure to say, F5.6 or F4 with my gevabox (which only goes up to F8), if my lightmeter only gives me the option of those wider apertures. As far as I can remember from reading about it years ago this is a reasonable method of doing so.
...

For that type of ME it is simple. Every time you double the number of exposure you increase the total by 1 stop. Two exposures at f/8 is the same total exposure as one at f/5.6. To get the same amount of light as f/4 you need 2*2, or 4, exposures at f/8.

This will hold reasonably well, but chemical film does not respond in a totally linear manner. There will be some unevenness with this approach. The shadow areas will not respond exactly the same as the highlights. For modest buildups, 1-3 stops or so, it should be accurate enough in most situations. Much beyond that and things become a bit Trial-and-Terror, and every film will be different. In general, the deep shadows will not buildup as much as the mid-tones, and the highlights will buildup faster. Adding a few extra exposures to help the shadows can destroy the highlights.

 

[seany65]

Dwig, About this

'deep shadows not building up as much as the midtones, and the highlights will build up faster.'

am a right in thinking that means they'll be a bit underexposed compared to the mids and more so compared to the highlghts, so if there's any detail in the real shadows it may be lost in the photo?

 

[Dwig]

Dwig, About this

'deep shadows not building up as much as the midtones, and the highlights will build up faster.'

am a right in thinking that means they'll be a bit underexposed compared to the mids and more so compared to the highlghts, so if there's any detail in the real shadows it may be lost in the photo?

It's all relative, as dear Albert E said...

If, and only if, we use the mid-tones as a reference point then when a number of exposures are made to bring the mid-tones to the "proper exposure" then the shadows will be underexposed and the highlights will be somewhat less overexposed.

This "error" will be too small to be of consequence when doing 2,4, and perhaps 8 shot buildups. When you make a very large number of significantly underexposed shots the issue will begin to have a detectable effect on the final image.

 

[seany65]

Thanks for that info, Dwig. More or less just what i wanted to hear.

 

[seany65]

I've been wondering what to do if my meter gives me a reading of 1/15 at f8, considering that my widest aperture is f8 and I have a fixed speed that seems about 1/30?

Would I close to f11 and do 2 exposures on one frame at 1/30?

What about 1/8 at f8?

Would I close to f16 and do 4 exposures at 1/30?

These examples of readings are 'probably' 😱 way out, but in principle is this what I would do?

I suppose what I'm really trying to do, by using ND filters and multiple exposures, is get from a camera with a very limited exposure range of f8, f11 and f16 at 1/30 to a camera that can go from f4 to f45, or be able to use 1/30 in situations when 1/8 to 1/500 are called for by the meter.

Of course I understand that being an almost brainless talentless bozo, means I'm probably worng on most counts of the 'theory' I'm working with.😱