Tuesday Tuts: Frame Rate & Slow Motion

I’m back with another DSLR video tutorial for you! This week we’re talking frame rate. Do not get this mistaken with shutter speed! Consider that video is really just a series of photographs, shot and displayed in really fast succession – your brain interprets this as motion. Frame rate is how many of those photos are shot and/or displayed per second. It has a surprising impact on the appearance of your video, and can allow you to play with time in your videos in really awesome ways.

I was privileged to behold the International Fire Knife Championships this weekend, as part of an incredible “Weekend in Polynesia” event at Pearson Park in Anaheim. What an amazing spectacle – performers as young as 5 years old dancing with spinning, flaming knives! Josh and I shot some video of the event on our Canon EOS 7D so that we could show you some cool frame rate demos and tricks.

 

30 FPS:

Television (in the U.S.) and video is traditionally shot in 30 frames per second (fps). Actually, it’s  technically 29.97 fps, but common vernacular and Canon DSLRs round up.

 

24 FPS:

Film and movies are shot and displayed at 24 fps (actually 23.98 fps). Because this frame rate is associated with a high-end medium, footage at 24 fps is often perceived to look “better,” “more expensive,” or – somewhat more fairly – “cinematic.”

Can you see the difference? It might be tough with such fast motion! Sorry about that… but at least the action is cool. :)

 

One of the reasons I am a big fan of the 7D is that it has so many options when it comes to frame rates. I can shoot in 30, 24, or 60 fps, and 60 has the option to shoot widescreen HD (1280×720) or standard definition (640×480). The 5D Mark II – while an awesome full-frame camera – still can’t shoot 60 fps.

 

60 FPS and Slow Motion:

The big advantage of shooting at a faster frame rate like 60 fps is that you have the ability to retime or conform the footage to a lower frame rate to create smooth, beautiful slow motion.

If you simply take a clip shot at your normal frame rate – say, 30 fps – and set it to 50% speed, your editing program will have to create extra frames in between the ones you shot (frame blending)…

…or it will display each frame for twice as long, effectively using a very unfamiliar – and choppy looking – 15 fps.

Conforming from a faster frame rate is the best way to do slow-mo, because it uses exactly the frames you shot. Again, think of video as a really fast slideshow. Say you shot 60 photos each second for this slideshow, each photo then representing 1/60 of a second. But if you decide to change the duration of each photo in the slideshow to, say 1/30 of a second, your slideshow is now twice as long. Your video is playing at 50% speed.

If you have Final Cut Pro, conforming your footage is easy.

With Final Cut Studio, use Apple Cinema Tools to conform your footage to the desired frame rate. Warning: This is a DESTRUCTIVE, IRREVERSIBLE process! Make a copy of your clip in a “Slow Mo” folder or something! Open the copied MOV clip in Cinema Tools (not transcoded – this will only work on originals) and click “Conform” for a dropdown menu.

Remember – if you’re matching “24 fps” footage, choose 23.98. For “30 fps” select 29.97. Unless you have a really good reason to do otherwise.

With Final Cut Pro X, this feature is supposedly built right in to the Retime (Apple + R) command, but I can’t tell for sure if it’s a true conform or just more advanced frame interpolation.

I like to go to the extremes in these situations, so let’s take a clip of the winning Fire Knife performance, shot at 60 fps, and bring it down to 24 fps – 40% speed. (but keep the audio at normal speed!)

…How fun is that?!

Of course, you can have fun with subtle changes as well. Going from 30 fps to 24 fps (80% speed) tends to give a slightly smoother, dreamier look to footage. This could be good for bridal or boudoir fusion. Just be sure to disconnect the audio – slow audio makes everyone sound extra manly!

Try it out for yourself… and share links to your slow-mo videos here!

 

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