HIGH FRAMERATE, RIGHT FRAMERATE?
By: Tyson Birmann
Slow Motion can be a great way to use motion to achieve a particular purpose. It can make a shot more impactful, funny, informative, or just plain beautiful. The industry as a whole has gravitated to use a certain few “goto” slow motion speeds. Common slow motion speeds are 48, 60, 90, or 120. While these may be most common, any framerate above the “Project Framerate” will appear as slow motion when inserted into the edit. These framerates are the most common, but maybe not the best ones to use.
The truth is, Slow motion is great in theory when you are shooting on set. However, sometimes in the edit room, after you see the pace of the scene… it might just not work anymore. So then what. Let’s say you have this beautiful take with all the right movements so you want to use it, but at “normal” speed. Let’s also say that you shot it at 48fps, 60fps or even 120fps, what do you do? This can be a tricky process that may actually end up needing a lot more processing than you think. I’m going to let you in on a simple trick to keep your footage as flexible as possible for your final project.
I’d say 90% of the projects shot in the US are shot using a base frame of 23.976 Frames per second. This seems like a super weird number and I can go into that at another time, but for now… let’s just accept that there is a reason and move on. Some projects may shoot at an even 24fps, but it is really rare. This means that no matter what FPS you shoot with your camera, the project will always play that footage back at 23.976. This of course means that when you shoot a shot at 48fps you are seeing ROUGHLY 1/2 the speed of the way it actually happened in the world. It is the ROUGHLY that becomes the issue. The simple reason is MATH. (yeah… I hate it too) If you open your calculator app and enter 48 ÷ 23.976 you will get an answer of 2.002002002002002. Nice round number, isn’t it!? So why do you care? You don’t until you want to “ramp” or use that footage to normal speed. In your edit software you will have to figure out all the complicated math to get that to play ACTUAL real time at 23.976. I’m not sure that math and I’m not going to bother with it. So what happens if you just set it to 2x or 200% speed? close enough right? Wrong! Since 48 FPS is not evenly divisible by 23.976… there will be frames that will have to be dropped. Dropping these frames can cause subtle jumps in your footage. If the subject is fairly still, you might not even notice. Then again, if your subject is fairly still, why the hell are you shooting it in slow motion? In order to get this to look normal, you actually have to process this footage in a very special way and have the computer create new frames to fill that little gap. Some do it better than others and in the end you might not even notice. My advice is save yourself the hassle.