Special F/X: The Fast-mo/Slo-mo Combo


Youve probably seen it used a lot in TV commercials. Its the effect where a sleek new car races toward the camera at high speed, then shifts into super-slow motion so the audience can get a good look as it glides past. The camera pans as the car slowly moves by, then the car explodes back into high speed as it races off into the sunset. What a cool effect! It must cost millions to create such a nifty looking, artsy shot, right? Nope. Its actually pretty easy and affordable. All you need is a camcorder with high-speed shutter control and a nonlinear editing system. The rest is post-production trickery.


The Shot

To make the effect look as good as possible, youll need to shoot with the edit in mind. Shooting with high-speed shutter allows your camcorder to record images with less motion blur, making for crystal-clear still images and crisp, slow-motion replay. A high shutter setting will add a strobe-like effect to the edited sequence. You may wish to shoot your footage twice. Once with high-speed shutter, once without it.

This effect plays well when shot from a low camera angle. Select a position next to the road, a safe distance from the vehicle, and set your zoom where youd like it to be as the car whips past. A quick pan will provide all the motion your shot needs. For a creative variation of the shot, add a wide-angle lens adapter to create a sense of distance and add some artsy distortion to the shot.


The Car

Instruct your driver to start some distance away, and drive at a steady speed past the camera and off into the distance. We have found that the effect works well with speeds between 35 and 55 miles per hour. You may want to record several passes at various speeds and lens settings so you can choose from a variety of takes in the edit bay.


The Trick

While the exact buttons you push will differ depending on the editing software you use, the steps are the same regardless of your system. Once in the edit bay, capture the raw footage to your NLEs hard drive. Select the clip youre going to use, then place it on your editing timeline. Divide the clip into three parts by cutting it with a razor tool at the points you want the speed of the clip to change. Your original shot should now be a combination of three separate clips. Be careful not to trim your clips at the points where they meet. These "match-frame" edits are essential for the effect to work properly. At this point, the three-clip sequence should play back as one seamless shot. If it doesnt, one of your in or out points has been moved. Delete the clips and start again.

Next use the speed tool in your editing software to apply a slow motion filter to the center clip. Because the last frame of the first clip matches the first frame of the slow-motion clip, and the last frame of the slow-motion clip matches the first frame of the third clip, the transition will be seamless. When you play the sequence now, you will see the complete effect as it plays fast, then slow, then fast again.

The key to this effect is the combination of match-frame edits and speed filters. The order they come in is up to you. You may wish to add a high-speed effect to your first and third clips. Or you may wish to make your first and third clips slower and your middle clip faster. The applications of this technique are limitless. You can try it on a pan, tilt or zoom for a cool variation. Now that you have the secret, well leave the magic up to you.

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