Techniques for preventing film movement during long exposures?

What is your method for preventing film movement during long exposure?

Ries!

Remember, if your tripod technique is lacking, it doesn’t matter how securely your film is sitting in the holder, or your holder in your camera. Thanks to the big trees in my region (think Sierra Redwoods & Douglas Firs), the ground where I set-up is often soft and pliant. That means the tripod doesn’t only sink and settle, but shakes when walking near it. This doesn’t even get into other sources of vibration, like wind or water current. My wooden Ries J-600 + J-250 head = improved stability & less film movement.

search ATG tape on this forum.

Film movement only? Homemade 4x5 vacuum film holders I've built. Not necessary for normal photography but essential for astrophotography.

Just tap the the bottom edge of the film holder before inserting into the camera to drive the film downward into the lowest edge of the film holder. No high tech gadgets needed. Of course, this assumes the camera (and film holder) are at least somewhat vertical, not pointed downward at an acute angle, which could allow for bowing... not "that much" with 4x5 though.

Tap the holder before loading it into the camera to ensure that it well-seated and will not shift mid-exposure.