Film shifting in holders

[Michael Veit]

I've been getting ghosts on my long exposure shots. After eliminating all other possibilities, I've concluded the film is shifting in my holders during exposure. Each holder is stored in plastic bags and I can well imagine there are temperature change issues which makes the film contract and settle as I expose for longer times in the winter cold. So what's the best work-around? Would it be enough to rap the holder to make sure the film is seated properly or would the use of double sided tape work better?

[Tim Curry]

It sounds like a shift due to cold would be taken care of by allowing the film to cool to ambient temperature first, then giving it a small rap on the bottom edge to make sure it has settled. This should take care of it if the cause is shifting. Are you sure it isn't flare from inside the camera body itself or a bellows leak?

The other thing I have heard, but never found, is that pulling a dark slide quickly in very cold weather can cause the discharge of static electricity which "sparks" across the film's surface. Pull the slide slowly to be sure this isn't happening as well. We don't usually have that problem in Tucson, but it doesn't hurt to be sure.

[Michael Veit]

Tim,

It's not bellows leak or flair -- I'm an expert at both ;-) No, it's always just a vertical (read gravity) offset of the image as a double. Sometimes the double is faint suggesting the neg shifted late or early in the exposure, sometimes the double is almost equally strong, indicating a mid-exposure shift. Both images are sharp, but their off-set varies, but is never greater than that one millimeter play that film has within a holder. Like I said, I'm as confident that I can be that I've narrowed down the source of the problem.

I, too, favor the "rap" idea. I just thought I'd troll (bad choice of word) for other solutions too.

Thanks.

[Carl Weese]

I've found this problem is apt to be caused by sudden change in humidity, causing the film to expand and buckle. Morning shoots in the fog are especially vulnerable. As the moist air warms up, film and holders are still cool and dry. The only answer I've found is to insert the holder, pull the darkslide, and wait a full minute before starting the exposure.---Carl

[sanking]

The position of film can definitely shift in some holders during long exposures. I have encountered this problem several times during long exposures of five minutes or more, and in each instance it was a case of the film literally dropping down vertically in the holder. The displacement was not great but more than enough to ruin the image. The only cure I have found for this is to rap the holder smartly before inserting it into the camera back in an effort to make the film drop before beginning the exposure.

Sandy King

[james mickelson]

This should be common practice by all LF shooters. Just get in the pratice of tapping the holder on your hand before inserting it into the camera.

[Michael Veit]

Thanks for all the replies.

James,

"should be common practice by all LF shooters."

Yeah, well it always takes me a couple years to discover what common practice should be ;-) In my defense, this is the first winter I've used plastic bags (that delayed common practice thing again) and I'm sure that makes the temp shock all the worse.

[james mickelson]

I know what you mean Micheal. It takes me a long time to make adjustments to my routine............routine. I knew about and even occasionally practiced tapping the side of my holders before inserting them (and that means tapping them again when turning them over to shoot the same shot again on the reverse side for a dupe) but didn't do it consistently. Until John Sexton made a point of telling his workshop that it was his standard practice and why. I know what you mean about shooting in cold weather. I use plastic bags for holding all of my film too. But I seldom shoot in cold weather so when I did the first time, what a shock. A few of my images were out of focus and it was clearly due to film shrinkage. A novelty at the time. Now I let the film stay in the air for a few before pushing the release in case of cold.

[Michael Veit]

James.

"A few of my images were out of focus and it was clearly due to film shrinkage. "

Funny, because I just came back to the thread with the idea that even un-shifted film could affect focus as it shrinks. When one measures sparpness of a lens in the 70 - 90 l/m range, it wouldn't take a lot of negative contraction to mess with things. It seems a combination of rapping and letting the film sit to get down to temp before opening the shitter is needed for best results.

[Michael Veit]

...um, that should be "shutter." The film-shitter interplay only happens after I view the proofs -- different part of the process entirely.