Slow Motion Mid-Take

[Luke Mascioli]

I've always wondered how, in some films, they'll be moving through in regular 24fps but then all of a sudden the shot smoothly slow down in the middle of the take. It’s almost as if they shoot at two frame rates at the same time and seamlessly transition between the two. 

How is this achieved? By shooting at a particular frame rate or using Al technology? 

 

[Mark Dunn]

I'm not a cinematographer but will take a shot at this.

If on film, the newer cameras (Arri 435?) can ramp up the speed and open the iris or shutter to match so it's unnoticeable. On digital the take will be acquired at the higher framing rate and the required part extracted at 24.

Edited July 7, 2023 by Mark Dunn

[Joerg Polzfusz]

Hi!

Speed ramping is normally done in post. The way to do it in Adobe Premiere Pro is explained here:

https://motionarray.com/learn/premiere-pro/premiere-pro-speed-ramping-tutorial/

IMHO the results are better when shooting the whole scene in SloMo and then letting the video editing software skip the obsolete frames. But this depends on the camera and the software.

[Joerg Polzfusz]

When shooting with S8, you would need to do it in camera with an additional tool like the http://cineassist.filmcurl.com.  But be aware that this heavily depends on your camera.

[Robin Phillips]

these days its usually just shooting at the slow mo rate the whole time, and doing the speed change in the computer. on film cameras like the 435 you could speed ramp while maintaining exposure during the take with the right controller, which can be really cool, but its tricky to nail and expensive if blowing through tons of 35mm

[Simon Wyss]

Nothing new under the sun. With the 1961 Bauer 88 L Zoom you could pull the trigger from normal run to a 64 fps override, the auto iris compensated for the change, and that wasn’t the only 8-mm. camera to offer this.

[Uli Meyer]

For a speedramp with an Arriflex 235 you use an  iris control unit. Open iris for the slow motion part and close the iris as it ramps down to 24fps. Using the iris method changes the depth of field as you ramp. If you use the shutter control of the 435, wider angle at slow mo and back to 172.8 for 24fps, the depth of field stays the same.

We did the Arriflex 235 speedramp here at 6:27

 

Edited July 8, 2023 by Uli Meyer