Double image when making long exposures

[chris jordan]

Hi again friends. I'm still having the double-image problem when making long ex posures, and have eliminated the possibility that it's a bellows or pinhole issue. Others have mentioned having the same problem, suggesting that the film may be "popping" during my long exposures, due to being exposed to the air after bei ng inside the film holder.

I have another theory that I thought I'd run by you to see if it has any merit ( any film manufacturing experts out there??). I've only had this problem when ma king long exposures, in dim light, with small apertures. So, what I'm wondering is, if there is some kind of internal reflection going on inside the film, that only becomes visible on the film when the light levels inside the camera are ext remely low? What I'm thinking is that the image might be reflecting off one of the emulsion layers, or the back of the film. The double image is always just s lightly offset from the "correct" image-- maybe 0.5 mm or so, and when using fro nt rise it becomes more pronounced toward the bottom of the film (i.e., the imag e area that's furthest from the center of the lens, and the most susceptible to such a reflection).

The reason I've come up with this is, my film is frequently exactly the same tem perature as the ambient air because I backpack with my camera, so the "popping" issue likely doesn't apply. One morning I found what would have been an all-tim e killer image in the rainforest, and just to make dang sure I got one good orig inal, I shot all of my film on the same image-- 16 sheets, and EVERY SINGLE ONE had the identical double image problem. My lens, bellows, lensboard, aperture, etc., are all pristine, and I always tap the film holder several times to lodge the film in place. I can't think of any other thing that it could be.

Thoughts, similar teeth-gnashing experiences?

~cj

[Ed Buffaloe]

It seems to me that if every sheet has the same double image, there is some problem inherent in the camera or lens. I won't speculate as to what. Have you tried borrowing another lens to use? Or borrowing another camera to use with your lens? That may be the only way you'll figure it out.

[Chuck_1686]

Not sure my logic is right here but I'll toss this out anyway. It would seem like if reflections are the problem that they would also be a problem on bright days when using short exposures. I seldom see this problem with 4x5 but often with 8x10. Never have seen it with 2 1/4 x 3 1/4 sheet film. Mostly on hot humid days with long exposure times. I've blamed it on the film shifting during exposure. The double image is usually near the edges. Maybe I should let the camera sit for a time after I pull the dark slide. Then again maybe there is something about reflections in low light vs. bright light that I'm not seeing. Chuck

[Carl Weese]

The popping issue may not have to do with temperature, but humidity. Were these pictures made in misty or foggy conditions? I've run into this repeatedly with my oversize cameras on foggy days. I think that it is the bellows-full of humid air that the film from the plastic-wrapped holder is suddenly exposed to when the darkslide is drawn. The sudden absorbtion of humidity may pop the film position. The only solution I've come up with for working with sheet film and long exposures in humid conditions is to pull the slide and wait a minute or more before beginning the exposure. I have done this a few times successfully but don't know if it will be a permanent answer to the problem. Obviously, if your popped negs were from the Mojave desert this analysis would not apply, but since you mention a rain

[Ken Burns]

Is the 0.5mm offset of the image always along a vertical axis? If it is, I would suspect that the film crawled. That means that the film moved in the holder during exposure. I always avoid that possibility by tapping the holder in the palm of my hand before inserting it into the camera to make sure that the film is moved to the lower edge of the holder.

[Dave Anton]

Chris, I would also suspect that your problem is the humidity (the emulsion absorbs moisture making it pop outwards). Leaving the slide open for a while will probably solve this. However, the fact that it happened to all 16 sheets of film, in exactly the same way is a bit concerning. Does this happen only with long exposures, or do you see this with short ones as well? Because maybe your lense is projecting a second image onto the film.

I can't see it being internal reflections as they are not focussed back onto the film. Reflections would result in general flare and loss of contrast.

[Robert A. Zeichner]

I have to believe this problem is due to some optical abnormality. The film can't be moving as you have proven this to be just about impossible. Let me ask a few questions. What lens are you using? Are you using a filter? What kind of filter is it? Is it on the front or rear of the lens? You say the problem seems to become alinear when you employ rise. If the offset grows larger the closer the projected image gets to the outer limits of the image circle, might this indicate something amiss inside the lens? Has the lens ever been worked on? I'm just throwing out some things to consider for the purpose of getting everyone to think about every possible oddity that could be at the root of your problem. I don't believe it could be related to light reflecting off the film or inside the camera as this reflection would be totally diffused and not result in a focused image back on to the film.

[Doug Paramore]

Chris: Try this. Put a piece of double-sided tape in the center of a film holder and tape the center of the film to the holder. It will push the film outward a bit, but that won't matter. Then make an exposure as you do when you get the double image. That should let you know if the film is popping. I still think you have a camer or lens problem. I don't live in Seattle, but I live on the south side of Alabama and most of the time our air is moist enough to drink. I have never had the problem you are experiencing while I am shooting 4x5. I would try, as another poster suggested, to borrow an identical lens or try your lens on another camera. These type problems can make us want to take up golf, but I think you can find the solution if you try keep up the search.

Regards,

[John H. Henderson]

I was going to ask what Robert did - what lens are you using? I'm thinking the lens might have ghosts that for some reason become more apparent when the reciprocity fails.

I'm having a difficult time believing that the film is sliding in the holder almost exactly the same way every time.

[Ken Burns]

Chris:

Film movement in the holder is actually a very common problem, especially when you are working with long exposures. Anyone who has very much studio experience working with the long exposure times dictated when working with hot lights is well aware of the problem. Those who are knowledgeable are well aware that it is almost mandatory to tap the film holder lightly in the palm of your hand before inserting it into the camera in order to make sure that the film has fallen to the bottom (which side of the holder that is the bottom depends on whether one is shooting a horizontal or vertical composition). Doing so will prevent the gravity-induced movement.

If you will hold the film holder in a horizontal plane parallel to the ground, you can hear the film move around inside the holder if you quickly move it back and forth from side to side.

Robert Mapplethorpe has a "famous" portrait of a princess from somewhere in Europe that has the double image you will get if the film moves during exposure. If your double image is similar to one he got, then you problem is definitely film movement in the holder during a long exposure.