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In 1980 I photographed the beginning of the main eruption. I was shooting Kodachrome 25, and quickly made 6 good exposures. Then my winder jammed and I made a triple exposure. Who can separate those 3 images?

That was the 20th roll of film I ever shot

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    \$\begingroup\$ Would be useful (and very interesting) to see that image. \$\endgroup\$ Commented Jul 3, 2020 at 9:18

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You cannot undo multi exposure on film nor separate the exposures from one another.

But why not keep the triple exposure image as it is? I mean, it has an artistic value, the photo tells a story. The moment the big catastrophy happened, you experienced a smaller 'catastrophy' with your camera. I think that's an interesting connection. Maybe give the photo a fitting title.

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  • \$\begingroup\$ 3x exposure on Kodachrome is probably burned so white there's almost no image on that frame. \$\endgroup\$
    – Zeiss Ikon
    Commented Jul 3, 2020 at 15:38
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As @Matt has said, there is no way (at least short of NSA or NASA level software) to separate multiple exposures on film.

In your case, it's worse than that. Kodachrome, as a slide film, loses information when overexposed (much the way negative film loses information when underexposed), and 3x exposure (about +1.5 stops total) is well out of the exposure latitude for Kodachrome. It's as if you'd metered that frame for ASA 8 instead of 25. Especially the lighter areas of the frame (sunlit portions of the ash cloud, for instance) likely contain no dye at all, no information that could be teased apart.

Even in darker parts of the frame, where the image isn't completely burned white, there is no reference point to separate the three overlaid images. The process you're after is called "deconvolution", but doing it in a way that produces something close to the original image is like correcting the First Light images from Hubble, before astronauts installed the optics to correct the hyperbolic primary mirror -- it requires having a pretty close idea of the aberration that damaged the image in the first place. In the case of a multiple exposure, that isn't possible. All you'd wind up doing is using the triple exposure as a guide to create a pixel-by-pixel hand-drawn digital image -- the task of at least hundreds of hours.

Take comfort in the fact that you have six more frames of the St. Helens eruption than I do (I was three hundred miles away in Idaho at the time), six more than almost every other photographer on Earth (not even counting those who weren't born yet).

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  • \$\begingroup\$ Thanks for the info. The original slide is very thin. I assumed that moden software would just click and "deconvolution" would happen. Now I know. After waiting 40 years to ask about this, I shall now patiently await the time I happen to encounter a NASA image technician. I certainly do hope that person was not party to denying the 'Martian Face'. \$\endgroup\$
    – Robert R
    Commented Jul 6, 2020 at 20:21
  • \$\begingroup\$ The people who did the work on the Cydonia features are already retired, most likely. The ones you want now are the ones who keep demonstrating that Curiosity, once again, has not photographed anything pointing to intelligent life leaving its trash around the rover's operating path. Hopefully, they won't laugh in your face -- I only included NSA and NASA because I'm not sure exactly what they can do (especially NSA -- NASA is generally pretty open-seeming). \$\endgroup\$
    – Zeiss Ikon
    Commented Jul 7, 2020 at 11:14

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