Undoing a double exposure.

[randalp33064588]

I accidentally set my camera to double exposure; 12 shots ended up as 6 double exposures. Is there any way in LR that I can reverse this - i.e., sort out the two separate exposures in a double exposure?

[JP Hess]

I will admit that I am totally ignorant about double exposures. I have never attempted to do that. However, as I understand it, a double exposure would be a single file comprised of two exposures. So what it seems to me you are asking is for Lightroom to somehow split a single image into two separate image files. There isn't any provision for such magic in Lightroom Classic or Lightroom.

[Conrad_C]

If the photo is in a flattened file format such as JPEG, then the double exposures probably can’t be separated. For example a pixel might be 40% black, but common photo software would have no idea how many percent originally belonged to image A and image B.

I haven’t used a digital camera that saves double exposures, but if you are very lucky, the camera saved them in a layered format where the two images still exist as separate layers in the file. If so, it might be possible to pull them apart, but that is not a feature of Lightroom Classic. If the camera comes with its own image processing software, see if it allows editing, remixing, or separation of that camera’s double exposures.

[richardplondon]

In all cameras I have used, Multiple Exposure means the inextricable merging of two (or more) photographs - this feature being disabled when set to Raw, so reserved for JPG. There are recently invented features (common with cellphones) whereby sequential frames from a single shutter-press get captured as a sort of 'movie', that lets you later vary what output image is constructed from those frames (or select between them when the subject is moving). But Multiple exposure is not of that sort and emulates a much older film-based technique that involves completely different shutter-presses being treated as one. So the output is a single, standard image file that does not retain the different shots as different shots.

If there is (say) a featureless white or black area in one of the shots, then something of the other shot could in principle be recovered just within that one area of the frame - but Photoshop would be much the better environment for exploring that, than Lightroom would be. In almost every case though, this sort of accident is (sad to say) not reversible.

[randalp33064588]

Thank you all for your responses. As usual, I realized only too late that I have not provided all the relevant info.

My camera saves RAW (actually, DNG) files  to the memory card. I first noticed these double exposures with I checked one shot in the playback mode - which of course is an internally-generated jpeg, but only temporary and not stored on the memory card.
When I imported the images into LR Classic and view them in the develop module, they show as the double exposure. But (as I understand it) the images are still in DNG form at that point (that's what the label says). But it is only ONE DNG file.

I was hoping there would be some way for LR Classic to separate out the two meant-to-be individual images. But it sounds improbable.

[richardplondon]

If these DNG images have the same expected file size that would be seen with a standard exposure, then there doesn't seem to be anywhere that a separable pair of images could be "hiding". Out of curiosity - what model of camera?

[randalp33064588]

Hmmm - another good point that I had not thought of. You are right - the
file size on the doubles is the same as the single exposures. So - I guess
the second exposure data for each pixel was combined with the original
data. I found one double where one exposure was landscape and the other
portrait - the combined double is portrait, but I do not remember which
exposure that was.
This camera was a Pentax K-1 mii - the top of their line. The selection for
multiple exposures is on one of the buttons on the 4-way controller, the
same button used to choose single shot, multiple shot, bracketing, etc.
That day I was driving with two friends and three dogs, and had no place to
put my camera except wrapped in an old shirt in a crate in the rear with a
bunch of junk. I'm thinking that after one stop I neglected to turn the
camera off, and it bounced against something hard enough to activate that
button.
My "lesser" Pentax K-50 requires entering the menu system to activate
multiple exposures.

[Conrad_C]

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@randalp33064588 wrote:

I was hoping there would be some way for LR Classic to separate out the two meant-to-be individual images. But it sounds improbable.

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That’s correct, it’s improbable, mostly because double exposures are not a typical feature of most digital cameras. Only a few cameras support them, using proprietary methods, so most photo editors (from both Adobe and other companies) will not attempt to support that feature.

That’s why I mentioned earlier that your best bet is to check the editing software provided by the camera manufacturer (if they provide that), because being well-matched to the camera, it has the best chance of being able to pull them apart. But, if the camera saves double exposures as merged images, not preserving the original two exposures separately, then no software will be able to pull them apart.

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@randalp33064588 wrote:

the double exposure. But (as I understand it) the images are still in DNG form at that point (that's what the label says). But it is only ONE DNG file.

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I agree with richardplondon…DNG is a container format, so it’s probably possible for it to store multiple images, but the camera would have to actually save it that way. And I have the same question he does: Which camera is it?

[Bob Somrak]

My Canon 5DMark3 saves multiple exposures as RAW and you have a choice of saving or not saving the RAW  images that make up the multiple exposure.

[Conrad_C]

Thanks Bob, that’s exactly the kind of example I meant. I was unable to be specific because I don’t own a camera that does double exposures in camera.

[Bob Somrak]

@Conrad_C 

You are not missing anything if your camera doesn't have it.  ; ).  I tried this feature when I first got the camera and I just checked again to see if it was doing it in RAW and saving all the exposures so that is only twice in the life of the camera that I used the feature.  I find it much more practicle to just shoot the images and do the FEW multiple exposures I create in Photoshop.

[randalp33064588]

Thanks everyone for your responses. I have to agree - the best way if one wants multiple exposures is to combine them in post-processing. The sole advantage I can think of for the Pentax system is it does give one the option of splitting the metered exposure between however many shots one is combining. Which I remember being the instruction for the old film days.

[ManiacJoe]

Late to the party.....

Lots of good info here already about what is going on and the inherent limitations.

In general Lightroom does not do layering and the like. Thus, Lightroom will probably not be able to separate out the individual images even if the DNG file contained them. However, Photoshop does do layering and the like. Thus, if the individual images exist, maybe Photoshop can see them separately. (Lots of if/maybe/possibly stuff going on here.)

[Chrisn N]

I know this is an old thread. As AI advances, it just might be possible in the future to separate them. Time will tell. 

Kind regards

Chris

[Conrad_C]

I know this is an old thread. As AI advances, it just might be possible in the future to separate them.

By @Chrisn N

Actually, if the double exposure is a raw file, it might be worth trying the new window reflection removal feature currently available for Technology Preview testing in Adobe Camera Raw 17. Adobe trained AI to recognize the difference between a subject and window reflections in front of it in the same image, separating them into two clean images. That technology might help separate the two images in an in-camera double exposure. Even though window reflections and an in-camera double exposure aren’t exactly the same thing, it would be worth trying.