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2X Frame Rate to Set Shutter Speed Rule...exception?

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Zack Mulvaney
2X Frame Rate to Set Shutter Speed Rule...exception?
on Nov 25, 2011 at 9:11:30 am

I want to shoot some vid on my T2i at 60fps and then conform it in Final Cut Cinemal Tools at 24fps for slow motion. Should I apply this doubling rule to the 60fps or 24fps? I'm hoping the 24fps, meaning I would only need to set my shutter at 1/50 for 60 fps (which is a lot more light coming in..which I want), but I never really understood the logic behind this rule so I don't know what Im potentially sacrificing if I screw this up.


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Peter Burger
Re: 2X Frame Rate to Set Shutter Speed Rule...exception?
on Nov 25, 2011 at 11:27:29 pm

Shutterspeed is more or less an aesthetic descision. With shutterspeed you create (or reduce) motion-blur. The "rule" ("shutterspeed should be 2 x framerate") creates a motion-blur that we are all used to and more or less instinctively accept as normal.

With higher shutterspeeds you'll get less motion blur which means every single frame (every phase of animation) is sharp. This can lead to strobing choppy motion, which can be a welcome effect, for instance if you want to show something very hectical.

With slower shutterspeeds you'll get more motion blur. With very slow shutterspeeds you'd get pictures with a dream-like quality.

The "rule" says: shutterspeed = 2 x framerate.

So when shooting 60fps you'd "have" to use a shutterspeed of 120 to get the "normal" motion blur. Even if you play back the footage with 24fps to create slomotion.

When shooting 60fps with a shutterspeed of 50 you'd get more motion-blur, than you might want to have.
IMHO the best way is to try different settings. Do a couple of tests and see what works for you and your footage.

In my experience, when just slowing down from 60fps to 24fps and you want a movie-like motion-blur, go with the "rule". When slowing the footage down even more with plugins like Twixtor, it might be best to use even higher shutterspeeds to eliminate motion to a greater extent, since those tools work best with little to no motion blur at all.

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"Tragedy is a close-up; comedy, a long shot." - Buster Keaton


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Zack Mulvaney
Re: 2X Frame Rate to Set Shutter Speed Rule...exception?
on Nov 26, 2011 at 3:17:49 am

EXCELLENT explanation -- thank you much!


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Jason Bowdach
Re: 2X Frame Rate to Set Shutter Speed Rule...exception?
on Jul 5, 2013 at 9:16:45 pm

Awesome reply. many thanks!


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