Question about old films . . .

[toymaker]

I'm not sure if anyone can answer this, and I'm not sure I even know how to describe it - or if there is a term for it.

 

Sometimes when you watch movies on an old film projector, the image will seem to "drop" for a second. I'm not sure if it's the film slipping as it goes past the lens.  Or maybe the speed isn't constant?  Does anyone know what the hell I'm talking about?  Is there an explanation for this?

 

 

Edited November 23, 2022 by toymaker

[TheGhostRider]

I'm not an expert on this but I think that's a common  thing on film strips for the film to be not be stable all the time. I have heard that sometimes it can happen due to the frame rate being tied to it in someway.

[goose]

From what I understand, the most common causes of film projector slipping are  momentary changes in tension (which can usually be resolved through lubrication of mechanical components) or flaws in the film's side notches.