5 ms·

> You can losslessly go from 120 to the other popular frame rates, including 24. Not true. Something filmed natively at 24 fps and a 180° shutter angle is vast

> You can losslessly go from 120 to the other popular frame rates, including 24. Not true. Something filmed natively at 24 fps and a 180° shutter angle is vastly different in terms of perceived motion than 120 fps converted to 24 fps.

lrem 7y ago
Are 1/48s exposures really that common in cinematography?
- dperfect 7y ago
  Yes. "By far the most common setting for cinema has been a shutter angle near 180°, which equates to a shutter speed near 1/48 of a second at 24 fps." [1] "A 180° shutter angle is considered normal." [2] [1] https://www.red.com/red-101/shutter-angle-tutorial https://www.red.com/red-101/shutter-angle-tutorial [2] https://en.wikipedia.org/wiki/Rotary_disc_shutter https://en.wikipedia.org/wiki/Rotary_disc_shutter
  - lrem 7y ago
    Oh. Right, replicating that exactly requires 240fps with fast shutter and discarding half of the frames. Which is a way more expensive proposition.
mrob 7y ago
If you shoot 120fps with 360° shutter angle you can downsample to 24fps with 144° shutter angle, which is close enough to the traditional 180°. And in any case cinematographers often vary the shutter angle, so viewers are already used to changes. Narrow shutter angle is common in modern action movies.
- dperfect 7y ago
  Yes, cinematographers do vary the shutter angle for artistic purposes, but that just confirms the fact that the amount of motion blur present in a film is a deliberate artistic decision rather than a side effect of using an "antiquated" frame rate. As for downsampling, I believe your math is off. 120 fps at 360° means each frame is exposed at 1/120s. Conforming that to 24 fps gives you the same exposure duration per frame (you're just throwing out 4/5 frames), so you're effectively at a 72° shutter angle - less than half of what's considered "normal".
  - mrob 7y ago
    I only said that 144° effective shutter angle is possible, not that you can achieve it by deleting 4/5 frames (which does give you effective 72° shutter angle). You actually need to delete 3/5 and blend 2/5 (and the 360° shutter angle of the 120fps source needs to be accurate enough that you don't see the join).

lrem 7y ago

Are 1/48s exposures really that common in cinematography?

dperfect 7y ago
Yes. "By far the most common setting for cinema has been a shutter angle near 180°, which equates to a shutter speed near 1/48 of a second at 24 fps." [1] "A 180° shutter angle is considered normal." [2] [1] https://www.red.com/red-101/shutter-angle-tutorial https://www.red.com/red-101/shutter-angle-tutorial [2] https://en.wikipedia.org/wiki/Rotary_disc_shutter https://en.wikipedia.org/wiki/Rotary_disc_shutter
- lrem 7y ago
  Oh. Right, replicating that exactly requires 240fps with fast shutter and discarding half of the frames. Which is a way more expensive proposition.

mrob 7y ago

If you shoot 120fps with 360° shutter angle you can downsample to 24fps with 144° shutter angle, which is close enough to the traditional 180°. And in any case cinematographers often vary the shutter angle, so viewers are already used to changes. Narrow shutter angle is common in modern action movies.

dperfect 7y ago
Yes, cinematographers do vary the shutter angle for artistic purposes, but that just confirms the fact that the amount of motion blur present in a film is a deliberate artistic decision rather than a side effect of using an "antiquated" frame rate. As for downsampling, I believe your math is off. 120 fps at 360° means each frame is exposed at 1/120s. Conforming that to 24 fps gives you the same exposure duration per frame (you're just throwing out 4/5 frames), so you're effectively at a 72° shutter angle - less than half of what's considered "normal".
- mrob 7y ago
  I only said that 144° effective shutter angle is possible, not that you can achieve it by deleting 4/5 frames (which does give you effective 72° shutter angle). You actually need to delete 3/5 and blend 2/5 (and the 360° shutter angle of the 120fps source needs to be accurate enough that you don't see the join).