Help understanding high frame rate

[yummy_waffles]

I understand that your shutter speed should always be double what your frame rate is – 60fps = 1/120 shutter speed.

But what happens if I decide to use a shutter speed faster than 1/120 sec...say 1/500 sec?

This question is in regards to slowing down footage in post.

Thanks!

 

[AndreeOnline]

As you know, a small amount of motion blur helps "link individual frames together" into pleasing motion. If your shutter speed is too short you will get more like stroboscopic motion where your eyes can filter out the individual frames in a motion sequence.

However, as you shoot higher and higher fps, you will quickly reach shutter speeds that are freezing the motion anyway, e.g. 1/120 might already provide "frozen frames" (lacking motion blur) in many situations. BUT, since you are capturing many frames per second you will get smooth motion anyway.

Some tests suggest that as early as 60 fps, shutter isn't all that important—the framerate itself will make the motion smooth. It's dependent on the viewer. At 100fps or over you can use 1/1000s or whatever.

Lots of sharp frames can be advantageous in many situations like stabilizing or tracking footage. But it can also produce more of a video look where some of the "magic" of 24fps goes away.

 

[David Jimerson]

The shutter speed "shouldn't" always be double your frame rate. Your shutter speed should be that which gives your image the look you want.

If you're using a shutter ANGLE of 180 degrees, then the numerical shutter speed will end up being double your frame rate, but that's because the actual speed varies according to your frame rate. But you should only use 180 degrees if you think that particular angle gives your footage the look and feel you think serves your purpose.

As to the effect shutter speed has on the image, there's a brief demonstration of shutter speeds and their effects on motion blur in the excerpts reel of 24p & Frame Rates:

http://www.wrightsvillebeachstudios.com/24pExpts.zip

You'll see exactly what the shutter speeds you're asking about do in an image. They affect motion blur and also exposure.

 

[Bruce Watson]

I understand that your shutter speed should always be double what your frame rate is – 60fps = 1/120 shutter speed.

You might understand that, but I don't. While it might be true that for "normal" 24fps footage a shutter speed of 1/48 is often desirable, the relationship between frame rate and shutter speed is more complex than your stated understanding. Much depends on what you are trying to accomplish -- what "look" you want to create.

But what happens if I decide to use a shutter speed faster than 1/120 sec...say 1/500 sec?

This question is in regards to slowing down footage in post.

If you use a faster shutter speed, you get less motion blur in each frame. For a slow frame rate, this can make your footage look somewhat jumpy or stroboscopic. And using a faster shutter speed without a faster frame rate doesn't really help you "slowing down footage in post". If what you want is slow motion, a faster frame rate capture helps more than a faster shutter speed, in general.

Unless you've decided that a program like Twixtor is your friend. Then, a faster shutter speed can help Twixtor's interpolation a little.