Time Required for Larger Sheets of Film to Buckle

[eric black]

Im not sure if it was to cold or if I was because I was shooting long exposures (>60 seconds) but I had several instances of film with two slightly offset exposures while shooting some 4x10 images in West Virginia last week. I'm assuming the problem to be the film starting out flat in the holder and then buckling outwards slightly part way through the exposure in the absence of a darkslide to hold it flat. I typically shoot multiple sheets of each image so I know focus wasn't the problem as I did get some good images on other sheets from the shoot-that didnt buckle during the exposure. I also know that the camera didnt get bumped or blown as there was no wind and I pay pretty close attention to these things during the exposure-besides, the final product looked like two images composed, slightly off from each other. With my lack of a vacuum-back, Im wondering if there is a procedure to deal with this- ie does anyone have a set amount of time to allow film to equilibrate in the holder prior to opening the shutter? If so, how long does one usually wait?

[Drew Wiley]

Sometimes a rapid temperature change can cause film to slightly buckle. It's rare. For
critical 8x10 work I personally use adhesive-style holders, since this solves the issue of film flatness too.

[panchro-press]

Any chance the sheet was only partially under the holder's guide rail?

-30-

[eric black]

Any chance the sheet was only partially under the holder's guide rail?

-30-

I would believe that if I had a single instance of the occurance, but with 5 out of 20 sheets of film and not having problems loading these film holders ever before, I doubt it. Im guessing that I need to pull the slide and wait a minute or two prior to exposing the film for these longer exposures- Ill probably run some experiments with a sacrificial sheet or two of film this weekend.

[Vaughn]

I tap the holders to get the film settled. I have more problems with the film being in slightly crooked, then falling into its proper place during the exposure, than buckling.

Vaughn

PS...Was your camera pointed down?

[eric black]

I tap the holders to get the film settled. I have more problems with the film being in slightly crooked, then falling into its proper place during the exposure, than buckling.

Vaughn

PS...Was your camera pointed down?

Yes, in fact the camera was pointed down during the problem exposures- the film falling will definately be checked during my experiments- thanks for the suggestion!

[ic-racer]

I would believe that if I had a single instance of the occurance, but with 5 out of 20 sheets of film and not having problems loading these film holders ever before, I doubt it. Im guessing that I need to pull the slide and wait a minute or two prior to exposing the film for these longer exposures- Ill probably run some experiments with a sacrificial sheet or two of film this weekend.

I'm still experimenting on how long to wait. I had one the other week. Camera back tipped forward slightly. I let it sit 30 sec with the darkslide out. It was a 5 min exposure and the film shifted still.

For those 'lurking,' this phenomenon is diagnosed by seeing a double outline at the film edge, where the film holder casts ist shadow on the film. That is how you can separate this from tripod shift, oscillations from wind or the back sagging or something else happening during the exposure.

[Jim Noel]

When film is in a holder it is in an almost hermetically sealed enclosure. If it was loaded in a low humidity are, and then used in a high humidity setting, or vice-versa, the film will "Pop". How long to wait is always a question. When photographing at night I generally remove the dark slide with the dark cloth over the camera and wait two minutes before making the exposure. This may be overkill, but I don't have the "popping" problem with film up to 7x17.
Jim

[GPS]

You can wait forever. Once the film is buckled the smallest camera/tripod vibration makes it vibrate too - how otherwise in its unstable position?

[Vaughn]

When I have had film "fall" into place during the exposure, usually it will be one corner falling -- seen on the neg as sharp in one upper (usually) corner of the image and more displacement seen in the doubled image as one you go towards the opposite corner.

Other than that, it is those dang pixies in the holders!

Vaughn

[Michael L]

Hi Eric,

Very frustrating isn't it?

I do exactly what Jim Noel suggests "When photographing at night I generally remove the dark slide with the dark cloth over the camera and wait two minutes before making the exposure".

The critical point here is that you cover the camera with a dark cloth, you'd be surprised how un-light tight lens boards are. I use the MT 2000 with Linhof boards and not a single one of them is 100% light tight. I let my film holders sit for about 4 minutes before I take the shot. Most of my images are up to 60 minutes long and this method seems to work 99% of the time.

[eric black]

Thanks to all for all of the help/advice- guess I need to add another step in my process when trying to do these longer exposures on my 4x10. I never even thought of the film moving around in the holder as a possibility- now I know better!