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Overcranking Versus Undercranking
In this video, there are examples of “overcranking” in this comedy bit we did with Jamie Costa.
You may have heard the terms “overcranking” and “undercranking” before in relation to frame rate. But what do these terms mean and where do they come from? Well, the answer is actually pretty simple.
Overcranking and undercranking are terms that hearken back to the old days of film cameras that were operated by cranking a handle that manually rolled the film. As you can guess, this was not the most consistent method, which is why you will often notice that very old film clips will appear jumpy and may stutter between too-fast and too-slow. Whenever the operator would crank faster than 24 frames per second, he would be “overcranking” and the footage would appear slower and smoother because he captured more frames than normal. Conversely, if the operator cranked too slow, he would be “undercranking” and the footage would appear faster and jumpier because he didn’t capture enough frames.
Today we often refer to overcranking as “slow-motion” or even “slo-mo.” Undercranking is not nearly as common, and is referred to as undercranking about as often as it’s called “fast-motion.” The extreme end of undercranking is, of course, time-lapse which is shot so slowly that it is measured in seconds between frames rather than frames per second.
How They’re Used
So what is the practical difference of overcranking versus undercranking? As I mentioned before, overcranking makes footage look smoother in addition to slower, so it tends to give the subject a more dramatic, epic, or massive feel. In visual effects, normal-size explosions are often shot at higher frame-rates so that they can be added to big effects shots at the standard speed and give the feeling of a much larger explosion. For beauty shots with plenty of movement, such as aerials, a nice overcranked shot will add a peaceful or epic vibe. There’s also the classic use of overcranking simply to slow down time in a shot in order to convey importance, add suspense, give time for the audience to inspect the frame, or mirror a character’s psychological state.
Undercranking is used much less often and has more limited uses. However, it can be very handy in action filmmaking as it can transform normal-speed actions or even actions that have been slowed down for safety into fast, exciting shots. It’s not at all uncommon for race sequences and martial arts fights to be undercranked to add speed and intensity. A recent extreme example of this was Mad Max: Fury Road which undercranked many of its sequences, including the opening foot chase and nearly all of the car chase wide shots. Usually filmmakers try to hide this effect in order to keep the suspension of disbelief, but the effect was incorporated into the style of Fury Road, keeping the weird, jittery side-effects as another part of the crazy, high-octane style. As is also often the case, more extreme uses of undercranking often yield humorous results. The classic example is the iconic Benny Hill chase sequence, but really just about anything will look funny if you speed it up enough.
Of course, if you can’t decide whether to use overcranking or undercranking, you can always use a time ramp! Time ramps are an editing technique that allows you to gradually adjust the speed of a clip. For instance, you could show one person moving to punch another, starting out in slow-motion to build anticipation for impact, then ramp up to fast-motion until the fist makes impact with the face to show the speed and force of the hit, and then slow back down to slow-motion to show the shockwave of force that hits the victim’s face. Of course, time ramping can also just involve one artificial speed combined with normal speed, but it’s fairly common to see overcranking and undercranking together in time ramps. A great example of this is many of the fight scenes in “300.”
How To Use Them
So how can you achieve overcranking or undercranking? Well, for overcranking you’ll need a camera capable of shooting at a frame rate higher than your master frame rate. If you’re mastering at 24 fps and have a camera capable of up to 120 fps you could choose 30 fps for a very slight effect to smooth things out, 48 fps for half-speed, 60 fps for a pretty common slow-motion feel, 90 fps for a very slow feel, or 120 fps for a super-slow-motion look. Shooting in 240 fps and beyond is considered extreme slow-motion and is less common, but can yield some truly remarkable imagery with the right subject.
Undercranking, on the other hand, is best achieved in post-production. Because overcranking requires extra data, it must be done in-camera, but since undercranking requires less data, it’s often better to shoot at your normal speed in-camera and delete the extra data in post unless you’re 100% certain you want to undercrank the shot. If you undercrank in your editing system, you can simply speed up the clip and it will delete the extra frames. If you do undercrank in-camera, you should remember that, when mastering in 24 fps, the most you want to undercrank is to 21 fps if you still want to achieve a believable look. Of course, if you’re going for comedy or a real wacky vibe, undercrank to your heart’s content.
So there you have it, overcranking versus undercranking. Which effect do you find yourself more drawn to? Have you found any optimal techniques through experimenting, either in-camera or in post? Let us know in the comments below!