Frame rate change to digitized 8mm film

Harry-Britton wrote on 9/4/2023, 10:11 AM

Hi: I just bought a projector of sorts, that saves the movie clips to an SD card, but at 20 frames per second. I'm trying to change the frame rate to 16, proper for regular 8mm film. Everything I try either changes the number of frames, doubles some frames, etc. The stretching seems to appear closest to what I'm looking for, but then it adds frames, I guess because the 'project frame rate' isn't changing with the time.. I'm expecting the individual frames to be unchanged except for the slight increase in time each appears. So, the clips length will grow on the timeline, but each frame and the number of frames will remain unchanged. It sounds easy, but not working for me. It would be ideal if I could change the play rate to 80%, which would be 20 to 16 FPS.

Any pointers appreciated! Thanks

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Comments

mark-y wrote on 9/7/2023, 9:21 AM

Just a sidenote -- most early consumer film transfers in the late 1980s and 1990s were done with a five-bladed aerial (no lens!) projector captured to interlaced AVI, giving us the infamous "3:2 Pulldown," which is actually quite easy to reverse engineer -- even the progressive conversions that end up on Youtube can be unbaked if nothing terribly weird has been done to them.

3d87c4 wrote on 9/7/2023, 1:56 PM

I just tried to convert to AVI, 4fps with VLC, and it remains 20FPS.

How would I convert/export to a series of frames?

Render image sequence:

Robert Johnston wrote on 9/7/2023, 6:20 PM

I displayed my 8mm film on a screen with the original projector (Kodak) and then recorded the screen with a 29.97 fps camera. It still flickered in places. There's this little metal clip that is supposed to keep the film steady in front of the lens, but it would sometimes quite often start vibrating. It's not permanently affixed to the camera. Fortunately, the Flicker Removal fx in Vegas helped with that a lot.

EricLNZ wrote on 9/7/2023, 6:31 PM

@Dexcon Apologies for the confusion but I did say "the flicker would be unwatchable". I wasn't referring to the film image motion smoothness. That's another matter and I agree with your comments. My comment "So effectively you see 16 x 3 = 48 images per second which we perceive as continuous motion" was on reflection misleading". I should have said "So effectively you see 16 x 3 = 48 images per second which we perceive as a continuous image".

The flicker is of course caused by the blank screen between projected images. You don't see the image being dragged down by the claw ready to display as that would be very unpleasant to watch. Why projector designers made three blanks per frame instead of just one when the film is dragged down I don't know. Maybe it's an engineering issue, or helps reduce the heat on the film.

As for persistence in vision much of my old 16 fps Std 8 is of cycle racing and motion across the screen is smooth. So with film my vision is happy with 16 fps but not with digital which puzzles me. I find 25 fps digital jerky with movement across the screen so I shoot 50 fps. So with digital the 48 fps comment you mention makes sense. I gather it might have something to do with shutter angle.