24P & Shooting Fire CML-Cinematography Mailing List

Shutter Angles

A very basic question. I know that when a shutter is at 180 degrees, it is half open and half closed. My question is when a shutter is at lets say 210 degrees, is it 210 open or is it 210 closed.

Thank you for your time.
John

Open. You are "closing down the shutter" (and shortening the shutter speed) when you use smaller degrees, like a 45 degree shutter angle. Generally a 200 degree shutter, like in Panaflexes, is the largest shutter angle that I've found in 35mm movie cameras. Is there a 210 degree option on some camera out there?

David Mullen ASC
Cinematographer / L.A.

Hey guys, I learned this once before but I guess I forgot over time. I just wanted to make sure that when you open your shutter to 90 degrees on 35mm film you close down half a stop (shooting at 24fps of course)? 45 degrees would be a full stop? Also does anyone have any kind of chart that would list all the shutter angles and their stop differences, both in 16mm and 35? I've looked all over the net and I can't find anything useful.

Thanks

Vinit Borrison
Student Director/DP
Toronto, On.

Totally wrong.

When you close your shutter to 90 you need to allow an extra stop ie open up a stop.

When you close the shutter down to 45 you need to open up another stop or 2 stops open on basic.

It's a simple mathematical progression, halve the shutter angle and you need to give 1 stop more light, this applies every time you halve the shutter angle.

And next time you try to post the same message here and 3 times in Pro you'll be off CML for good.

-- Cheers

Geoff Boyle FBKS

Director of Photography
EU based
www.cinematography.net/geoff

There aren't many camera manuals or books that don't have this information. My AC manual is an old 6th edition and it's on p 162 - but I'm sure that David Samuleson's manual and others include it too.

Now . .

>when you open your shutter to 90 degrees

. . .from what angle? If from 180 degrees, then you are closing it, not opening it, and you must open the aperture one full stop. If you go to 45 deg, it's another full stop.
Every time you halve the exposure (i.e halve the shutter angle) you must open one stop. Every time you double the angle, you close down one stop.

You probably need to get one of those books and look through it.

Dominic Case
Group Technology Manager
Atlab Australia

Following up on Dominic's suggestion, last time I was in Toronto I noticed that the Ryerson bookstore stocks both the ASC manual and David Samuelson's manual... A student DP shouldn't be without either. Since good things come in threes, you might also try the Professional Cameraman's Handbook.

George Hupka
Director/DP, Downstream Pictures
Saskatoon, Canada