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Shutter angles


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#1 Andrew M Banks

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Posted 21 February 2008 - 11:51 PM

I notice that movie cameras have shutter angles in certain steps. Here they are, in degrees, with my guess for the reason for each. Please fill in my blanks and correct me where I'm wrong.

180 - standard shutter speed, 1/48 sec.
172.8 - at 24fps, yields 1/50 sec., for shots of TV screens in Europe
144 - at 24fps, yields 1/60 sec., for shots of TV screens in the U.S.
135 -
120 -
105 -
90 - half the standard shutter angle, so you can open 1 f-stop more
75 -
60 -
45 - one quarter the standard, so you can open 2 f-stops more
30
22.5 - one eighth the standard, so you can open 3 f-stops more
11.2 - one sixteenth the standard, so you can open 4 f-stops more
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#2 Saul Rodgar

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Posted 22 February 2008 - 12:35 AM

11.2 - one sixteenth the standard, so you can open 4 f-stops more


The narrower the shutter angle the more "choppy" or stepped subject motion appears on film. So it is not a question of "going to a narrower shutter-angle, so I can open up a stop." It is more a creative decision, like action sequences look more "real" or stylized with a narrower angle (certain battle scenes in Saving Private Ryan) and so on.
Usually the reasoning is more based on the look of the narrower shutter angle footage itself than the need to open up the lens. A good ol' ND filter would allow you to open up the lens without changing the look of motion on film.
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#3 Andrew M Banks

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Posted 22 February 2008 - 09:16 AM

Yeah, it's just that some of the steps made odd fractions, like 1/115.2 sec., so I was wondering if that was for avoiding flicker when shooting certain computer monitors or flourescent lights.
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#4 Saul Rodgar

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Posted 22 February 2008 - 12:32 PM

Yeah, it's just that some of the steps made odd fractions, like 1/115.2 sec., so I was wondering if that was for avoiding flicker when shooting certain computer monitors or flourescent lights.


Well, that depends what equipment one is using, of course. Square wave discharge lights are safe at most, if not all speeds. I have heard of issues with some Kino banks flickering at non- 24 fps camera speeds, so even the King of flourescents can be a pain as well . . . LCD monitors and projectors are also flickerless at most speeds. Although I once found one that "blinked" (certain colors changed) at 30 fps.

But yeah, I hear what you are saying. unfortunately, not all cameras have as great a range in shutter angle as the one you described above. Some, such as the Arri 435 ES, are capable of ANY shutter angle from 11.2 to 180 degrees, continuosly variable even as the camera is on.
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#5 Valerio Sacchetto

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Posted 22 February 2008 - 01:39 PM

some are just thirds of a "stop" (60, 75, 120...)
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