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shutter angle - what is it?

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Stephen May
shutter angle - what is it?
on Oct 24, 2008 at 11:09:59 pm

I need to come clean - I need someone to explain shutter angle to me. I do not understand it. I know what the shutter can do, I know that the faster the shutter, the crisper the shot, and the more the exposure is effected by reducing the incoming light, forcing the need to reduce ND filter, or open the iris to compensate. Shutter is great for fast action - so if any of this is correct, what is shutter angle?

Stephen May
Keystone Media Productions
Freelance Videographer


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Stephen May
Re: shutter angle - what is it?
on Oct 26, 2008 at 12:35:04 am

since posting my question, I've been researching the subject. I think I'm getting it.

I'm writing to thank Don Greening for his contribution on December 23, 2007 in a reply to Randy which included this link:

http://www.tech-notes.tv/Archive/tech_notes_035.htm

-s

Stephen May
Keystone Media Productions
Freelance Videographer


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Don Greening
Re: shutter angle - what is it?
on Oct 26, 2008 at 5:11:35 pm

I guess everyone's been quite busy over the last couple of days, Stephen. Sorry about that. I think Sony's reasoning behind providing a shutter angle option in addition to the usual shutter speed in the EX cameras is to accommodate those folks from the film world who feel more comfortable doing shutter adjustments with angles and degrees rather than the time value of shutter speed that video folks are used to.

An experienced film person is going to think: "Okay, in order to reduce motion blur when shooting 30p I need an angle of 144 degrees minimum." They won't think about the time value equivalent of 1/60th sec.

That's just my opinion, anyway.

- Don


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Craig Seeman
Re: shutter angle - what is it?
on Oct 26, 2008 at 5:24:26 pm

There's a real technical difference in the way shutter angle is implemented compared to shutter speed (although more of a convenience feature).

If the shutter angle is set to 180° it remains at that angle regardless of frame rate. You can shoot and 720p24 or 720p24 60 overcrank and not have to change the angle. On the other hand if you're using the fractional method you have to remember to change from 1/48 to 1/120 for example.

Basically angle remains constant relative to frame rate. With fraction you need to remember to change it manually to the new fraction.

Another way to put it. 180° at 24fps, 30fps, 60fps is always the "correct" fraction for the frame rate. On the other hand using the above numbers you'd need to use 1/48, 1/60, 1/120 to get the same "motion blur" (or whatever you want to call it).





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Don Greening
Re: shutter angle - what is it?
on Oct 26, 2008 at 6:24:38 pm

[Craig Seeman] "Basically angle remains constant relative to frame rate. With fraction you need to remember to change it manually to the new fraction. "

This is a really important consideration. Thanks for pointing that out, Craig.

- Don



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Stephen May
Re: shutter angle - what is it?
on Oct 29, 2008 at 12:57:35 am

Don, Craig, thanks. -s

Stephen May
Keystone Media Productions
Freelance Videographer


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