the mysterious double image

Compiled by Q.-Tuan Luong for the Large Format Page

One thing to do if you get double images that are offset by quite a bit is to look for pinhole light leaks in the lensboard or around the lensboard seat, or even perhaps toward the front of the bellows. You would probably only see the pinhole image if the lens was well stopped down so that the relative brightnesses were fairly close.

Another more common source of double images is film shifting in the film holder. I generally give the holder a rap after pulling the dark slide, to get the film to shift if it's going to. If there is a big difference in temperature or humidity, film can flex quite a bit when first exposed to the air in the camera - it's wise to wait a bit after pulling the dark slide before opening the shutter. If you only got a double image on part of the transparency, I'd suspect that the film shifted in the holder - sometimes it will only shift on one end, and so the registration is near perfect in one corner and is awful in the far corner. Further evidence would be that the offset is less than about 2 mm, the amount of slop the film has in standard holders.

Generally, I've found that having the tripod set on soft ground (sand, for instance) that shifts when I move results in soft images, not double images. Very long exposures are the exception, but I tend to open the shutter, carefully let go of the cable release, and move away right at the beginning of the exposure, and then just stay away until right at the end, when I step up and close the shutter. This results in the bulk of the exposure being done with the camera undisturbed, probably the safest approach by far.

Paul Butzi

You know, I remember having to do a major repair on that 5x7 bellows shortly after that. I have not had a situation like that since I changed to my Deardorff. I generally rap the holder before I install the holder in the film slot. Most of that is to move the dust to some area other than the clear zone 7 or zone 8 area of the neg. Usually never works, though. 8-((. Not a bad idea to smack it again after it is in the camera. However, that pin hole in the bellows sounds like what was working against me that day. As usual, Lee Carmichael

I've had some double images, some are overall, some just in part of the image (these are all with fairly long exposures). I have also read reports from several others that have seen the same problem with long exposures.

What I think is going on, is that the film itself is shifting or popping during the exposure. When the whole image is double, I'd guess the film shifted and when only part of the image is double, the film probably bowed or popped during the exposure. In at least one case, one corner was pretty sharp and the double image looked like a rotation around that corner which is probably a shift of only one side of the negative.

For a shift, the film may not have been firmly seated in the bottom of the holder. For a bowing or popping of the film or part of the film, I'd guess that it was due to humidity or temp changes as the film was freely exposed to air inside the camera instead of the somewhat air-tight film holder with a closed darkslide.

To minimize shifting, it may help to rap the lowest edge of the film holder (lowest as it will be oriented in the camera) against your hand a couple of times to make sure the film is already shifted if it's going to.

For popping or bowing, I read somewhere (I think it was a Compuserve posting by John Sexton from something he got from Kodak) that you need to remove the darkslide and wait something like 5 or 10 minutes (maybe it was even longer) before exposing the film to ensure that the film and air it's exposed to are fully equalized. Usually the light is changing too quickly for me to be willing to wait this long and my double image problems are rare enough that I just risk this. I also often make an identical backup exposure which has always been enough so far to avoid losing an image. It might be different for a commercial job especially one with artifical light where the light doesn't change. The added 5 or 10 minutes per exposure might be well worth it then, at least with long exposures.

John Sparks

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