5 ms·

I'll do you one better, which requires no special cameras (most have IR filters) nor double cameras or prisms. Shoot the scene in 48 or 96 fps. Sync the set li

I'll do you one better, which requires no special cameras (most have IR filters) nor double cameras or prisms. Shoot the scene in 48 or 96 fps. Sync the set lighting to odd frames. Every odd frame, the set lights are on. Every even frame, set lights are off. For the backing screen, do the reverse. Even frames, the backing screen is on. Odd frames, backing screen is off. There you go. Mask / normal shot / Mask normal shot / Mask ... you get the idea. Of course, motion will cause normal image and mask go out of sync, but I bet that can be remedied by interpolating a new frame between every mask frame. Plus, when you mix it down to 24fps you can introduce as much motion blur and shutter angle "emulation" as you want.

ryandamm 7mo ago
This is called “ghost frame” and already exists in Red cameras and virtual production wall tools like Disguise.
- actionfromafar 7mo ago
  You need to basically timecode/genlock the greenscreen "illumination LEDs" to the camera so the greenscreen lights up only exactly at every other frame. Not sure if there exists any off the shelf solution which can do that but if not it can't be super hard to cobble together.
  - cma 7mo ago
    https://evermorestud.io/retroreflective-chromakey-experiment/ https://evermorestud.io/retroreflective-chromakey-experiment...
amluto 7mo ago
Surely this makes your actors feel sick? And wouldn’t it make your motion blur look dashed and also cause artifacts at the edge of the mask if there’s a lot of motion?
- throwway120385 7mo ago
  You could strobe at some multiple of the sensor frame rate as long as your strobes are continuous through the integration period of the sensor and the lighting fades very quickly. This probably wouldn't work with incandescents but people strobe LEDs a lot to boost the instantaneous illumination without going past the continuous power rating in the datasheet.
  - amluto 7mo ago
    You mean do strobe, strobe, strobe, strobe, pause, pause, pause, pause? I bet that's at least as bad as holding the source on for the first four intervals and then off for the latter four intervals. In any case, if you actually have a scene bright for 1/24th of a second and then dark for 1/24th of a second, repeating, you're well within photosensitive epilepsy range. Don't do that to your actors unless you've discussed it with them and with your insurance company first.
    - actionfromafar 7mo ago
      So, shoot at 240 fps and strobe set lights for 1/240s and backdrop for 1/240s.
      - wlesieutre 7mo ago
        And if you want a slower than 1/240th second shutter speed, no you don't
        actionfromafar 7mo ago
        Or... you frame blend in Fusion or go full hog in Nuke. ( https://www.nukepedia.com/tools/gizmos/time/vectorframeblend/ https://www.nukepedia.com/tools/gizmos/time/vectorframeblend... )
- kibibu 7mo ago
  Incandescent and fluorescent lights already flicker at your AC power frequency. Just gotta be higher than that
ErroneousBosh 7mo ago
Corridor Crew cover this in one of their VFX breakdowns where I can't remember the film but it was supposed to be filmed on a rapidly rotating platfom. There were a large number of lights around it and each one was blinked on for an instant while the camera shot at an insanely high frame rate - something like 288 frames per second with twelve lights. This meant that after the fact you could pick any one of the twelve frames for that 1/24th of a second, to choose the angle the light was hitting at.
shdudns 7mo ago
Two problems: - It'll bleed on fast motion. Hair in the wind would just not work. - Incandescent lights are out. You could solve both by having two ghost frames shot very close to the real frame (no need to evenly space the frames, after-all) and using strobing a high powered laser. You'd need very fast sensor or another one optically on the same position.
- actionfromafar 7mo ago
  At some point higher fps solves it. Is 240 fps enough?
  - shdudns 7mo ago
    I dunno, I'm just an amateur photographer. The calculation isn't too hard though. The width of a pixel divided by the velocity of the subject on the sensor is the maximum delta(T) between real and ghost frames. But, again, you dont have to shoot faster. You just have to drop the 180-180 degree phase between a real and ghost frame to be 10-350 degrees. Then your 24 fps is capturing the background as if it were 870 fps
huflungdung 7mo ago
[dead]
eichin 7mo ago
Somebody recently used a variation of this to get good video of welding - basically a camera synced with a very bright (strobe-ish) light, brighter than the weld itself, so you adjust the camera to the ludicrous-but-consistent brightness level and get details of the weld and the surroundings. https://www.youtube.com/watch?v=wSUxK8q4D0Q https://www.youtube.com/watch?v=wSUxK8q4D0Q (Chronos "Helios", from early 2025)
dgently7 7mo ago
this is the approach that stop motion uses, except they get to keep the camera in the same place. its still not perfect because of spill from the background onto the foreground and requires additional masking and cleanup.

ryandamm 7mo ago

This is called “ghost frame” and already exists in Red cameras and virtual production wall tools like Disguise.

actionfromafar 7mo ago
You need to basically timecode/genlock the greenscreen "illumination LEDs" to the camera so the greenscreen lights up only exactly at every other frame. Not sure if there exists any off the shelf solution which can do that but if not it can't be super hard to cobble together.
- cma 7mo ago
  https://evermorestud.io/retroreflective-chromakey-experiment/ https://evermorestud.io/retroreflective-chromakey-experiment...

amluto 7mo ago

Surely this makes your actors feel sick? And wouldn’t it make your motion blur look dashed and also cause artifacts at the edge of the mask if there’s a lot of motion?

throwway120385 7mo ago
You could strobe at some multiple of the sensor frame rate as long as your strobes are continuous through the integration period of the sensor and the lighting fades very quickly. This probably wouldn't work with incandescents but people strobe LEDs a lot to boost the instantaneous illumination without going past the continuous power rating in the datasheet.
- amluto 7mo ago
  You mean do strobe, strobe, strobe, strobe, pause, pause, pause, pause? I bet that's at least as bad as holding the source on for the first four intervals and then off for the latter four intervals. In any case, if you actually have a scene bright for 1/24th of a second and then dark for 1/24th of a second, repeating, you're well within photosensitive epilepsy range. Don't do that to your actors unless you've discussed it with them and with your insurance company first.
  - actionfromafar 7mo ago
    So, shoot at 240 fps and strobe set lights for 1/240s and backdrop for 1/240s.
    - wlesieutre 7mo ago
      And if you want a slower than 1/240th second shutter speed, no you don't
      - actionfromafar 7mo ago
        Or... you frame blend in Fusion or go full hog in Nuke. ( https://www.nukepedia.com/tools/gizmos/time/vectorframeblend/ https://www.nukepedia.com/tools/gizmos/time/vectorframeblend... )
kibibu 7mo ago
Incandescent and fluorescent lights already flicker at your AC power frequency. Just gotta be higher than that

ErroneousBosh 7mo ago

Corridor Crew cover this in one of their VFX breakdowns where I can't remember the film but it was supposed to be filmed on a rapidly rotating platfom. There were a large number of lights around it and each one was blinked on for an instant while the camera shot at an insanely high frame rate - something like 288 frames per second with twelve lights. This meant that after the fact you could pick any one of the twelve frames for that 1/24th of a second, to choose the angle the light was hitting at.

shdudns 7mo ago

Two problems: - It'll bleed on fast motion. Hair in the wind would just not work. - Incandescent lights are out. You could solve both by having two ghost frames shot very close to the real frame (no need to evenly space the frames, after-all) and using strobing a high powered laser. You'd need very fast sensor or another one optically on the same position.

actionfromafar 7mo ago
At some point higher fps solves it. Is 240 fps enough?
- shdudns 7mo ago
  I dunno, I'm just an amateur photographer. The calculation isn't too hard though. The width of a pixel divided by the velocity of the subject on the sensor is the maximum delta(T) between real and ghost frames. But, again, you dont have to shoot faster. You just have to drop the 180-180 degree phase between a real and ghost frame to be 10-350 degrees. Then your 24 fps is capturing the background as if it were 870 fps

huflungdung 7mo ago

[dead]

eichin 7mo ago

Somebody recently used a variation of this to get good video of welding - basically a camera synced with a very bright (strobe-ish) light, brighter than the weld itself, so you adjust the camera to the ludicrous-but-consistent brightness level and get details of the weld and the surroundings. https://www.youtube.com/watch?v=wSUxK8q4D0Q https://www.youtube.com/watch?v=wSUxK8q4D0Q (Chronos "Helios", from early 2025)

dgently7 7mo ago

this is the approach that stop motion uses, except they get to keep the camera in the same place. its still not perfect because of spill from the background onto the foreground and requires additional masking and cleanup.