If you've played around with the manual controls of your camera – DSLR or other – you probably know a little about shutter speeds and the effect they have on your photos. If you set your shutter speed to be faster, your camera lets in less light (all other settings equal). Essentially, this freezes motion in a still photograph, assuming there is enough light to properly expose an image. So what does this mean in video?
The Basics of Shutter Speed
Nevit Dilmen's Windflower: Slower shutter speeds (right) suggest movement in a still photograph. Fast shutter speeds (left) freeze a moving subject on photograph.In video, shutter speed produces a similar effect as in still images. Slow shutter speeds result in blurred, smeary images; fast shutter speeds result in crisp, staccato-like images.
In video, we have a rule for choosing shutter speed so it's not to blurry and not unrealistically crisp. It's called the 180 degree rule. Because in video, unlike photography, the shutter speed is calculated in terms of degrees, or shutter angle.
Lets Get Technical
In a film camera, there is a 180-degree (half-circle) shutter that rotates and exposes the film to light. Therefore, in one frame, the film is only exposed to light half the time. That means that film shot at 24 frames per second (the standard in cinema – the “film look”) is the equivalent to 1/48th of a second because 1/2 the frame is exposed in a second. So the math to calculate the shutter speed for the 180 degree rule is relatively simple – at 24 fps, the shutter speed is 1/48 seconds, at 30 fps the shutter speed is 1/60th of a second and at 60 fps the shutter speed is 1/120 seconds. (See Tyler Ginter's Blog.)
But what if you want to break the 180 degree shutter rule? In combat scenes of Saving Private Ryan, the director used a shutter angle of 45 degrees to reduce motion blur and create a flickering look that intensified the action. A 45 degree shutter speed is the equivalent of 1/192 seconds at 24 fps because 24 multiplied by 360 (degrees in a circle) is 8640; divided by 45, you get a shutter speed of 1/192. You can do the math yourself, refer to a cheat sheet or experiment with various shutter speeds to achieve the look you like. (See the DSLR Guide at BHPhoto.com.)
Saving Private Ryan: Combat scenes in Saving Private Ryan were filmed at faster shutter speeds.If you want to create a natural-looking video, choose shutter speeds according to the 180 degree shutter rule. This means choose a shutter speed of 1/48 at 24 fps and 1/120 at 60 fps. Note that you may need to approximate with your DSLR because the exact shutter speed you want may not be available. You won't notice an obvious difference in the look of your video if you choose 1/50 of a second at 24 fps instead of 1/48 of a second. If you want a choppier, staccato-like look like in the combat scenes of Saving Private Ryan, choose a faster shutter speed – up to 1/192 seconds at 24 fps. Don't choose slower shutter speeds, as the smeary, blurred look just doesn't look good. Of course, that's an opinion, but a widely accepted opinion.