long exposure help needed

[h2oman]

Yesterday I did a 20 minute exposure, far longer than I've ever done before. My guess on exposure came out pretty well, but the camera moved. Here are the particulars:

Camera: Wista SP, tightened up all adjustments pretty well before the shot. 90 mm lens, so the bellows were not extended.

Tripod: Pretty beefy Feisol tripod w/ rubber feet, on a rough bedrock surface. I guess I should have checked where the feet were - maybe getting them into divots in the rock would help.

Head: Semi-beefy Benro ball head. I MAY not have really cranked this down.

Aperture: f32

I used a cable release and left it hanging during the exposure. I was in a cave, with no wind and no people coming by other than me when I left the camera and then came back.



The only ideas I have right now are to weight the tripod and remove the cable release and do the exposure by simply removing and replacing the darkslide with the lens open (to the desired aperture). I suppose I could remove the ball head and attach the camera directly to the tripod, but I'd rather not do that. I also don't want to purchase another tripod!




Any thoughts? Thanks!

[Jon Shiu]

Also make sure to tap the film holder a few times to make sure the film is settled at the bottom before shooting.

Jon

[Kevin Crisp]

Can you post it? It may be film popping not camera movement. Even occasional gusts of wind which do cause some camera movement are usually invisible on the negative, since the images strays a bit during the gust but spends 99% of the time in the original position. Seeing the image would be helpful.

[h2oman]

OK, guys, I'm thinking one of you is correct. You should be able to see in the crop I've attached that all edges that I can make out seem to be repeated twice, indicating that the position of either the camera or the film changed once during the exposure, with sufficient time time in each of the two positions to record those edges.

I brought the film holder form near the front of the cave, where the air is warmer, backtothe camera, whereit was cooler, just before making the exposure. It would likely behoove me to bring the holder back earlier and let it adjust to the temperature before making the exposure.

Thanks for your help.

PS Don't look at the image too long or it will make you dizzy!

[David Schaller]

Did you wait after you pulled the dark slide? I usually wait 30 seconds to a minute after I pull the dark slide before I trip the shutter. I doubt it's the shutter causing that much movement.
Dave

[Erik Larsen]

I think a bat landed on it while you weren't looking!

[Andrew O'Neill]

That looks like the film shifted inside the holder. That happened to me during a 2 and a half hour exposure once.

[Brian Ellis]

Given the facts you describe and assuming no other relevant facts that you haven't mentioned (e.g. incorrect focus or the camera being inadvertently bumped after it was focused, etc.) it would have been impossible for the camera to have moved unless there was a problem with the head. So either something happened that you don't know about or haven't thought was worth mentioning or the problem wasn't camera movement. Film moving in the holder is a pretty good bet. Did you give the top of the holder a good firm tap several times with your hand before inserting it in the camera to make sure the film was at the bottom of the holder? I think that's a good practice to follow as a routine matter, I did it every time I made a photograph and never had a problem with film moving in the holder.

[tuco]

With a 20 minute exposure, I doubt a little bump would even be recorded. I bumped mine on a 4 minute exposure once and when I developed the film you couldn't even tell.

[Peter Gomena]

I'll second film "pop", but I'll add the possibility of a little film curl from humidity change to the film over 20 minutes in a dank cave.

You also can put a piece of double-stick tape in the middle of the film holder if you know you're going to make a long exposure. Use just a 1/2" piece, and touch it a few times with your finger to decrease the tackiness.

Peter Gomena