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Limitations of a fixed 18 Deg. shutter?


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#1 James Steven Beverly

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Posted 10 April 2008 - 06:35 PM

My camera packages are all commiecams which means they have fixed 180 deg. shutters and I got to thinking, the Soviets built tough, reliable equipment but it's functionality was somewhat limited fir example US spacesuits were marvels of technological achievement, VERY expensive and custom build for each astronaut, however Soviet spacesuits were much cheaper, not custom made for each cosmonaut and were limiting in what the cosmonaut was able to do in them, so the Soviets simply limited the cosmonaut's mission parameters to what the suit was capable of doing. Not the most elegant solution to the problem but it worked reasonably well to achieve most of their goals. I plan to follow a similar strategy with regards to my productions. In general terms, what are the limitations of using a camera with a fixed 180 deg stutter, and are there exceptions and work arounds to any of these limitations? Thanks- B)
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#2 David Mullen ASC

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Posted 10 April 2008 - 06:54 PM

90% of what you are going to shoot will probably be 24 fps w/ a 180 degree shutter, unless you are into the "Gladiator / Saving Private Ryan"-esque short shutter look for fight scenes.

Your main limitation will be syncing to CRT TV sets on set to get rid of the roll bar, plus off-speed shooting under 60 Hz pulsing AC lights, unless you stick to safe speeds for 180 degrees.

Plus if you plan on taking your camera into a 50 Hz country.
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#3 Michael Nash

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Posted 10 April 2008 - 07:04 PM

In general terms, what are the limitations of using a camera with a fixed 180 deg stutter,


Any issue that involves synching the camera's frame rate to some other real-world flicker -- HMI lights, fluorescent lights, TV screens, and so forth. Since your shutter is fixed, the only way to synch to something with an interval that doesn't neatly match 1/48th second at 24 Hz. is to change the frame rate -- which means losing synch sound.

Shooting 50Hz. lighting at 24fps requires a 172.8 shutter to avoid flicker. Shooting 25fps under 60Hz. lighting requires a 150 degree shutter.

Shooting a 60 (59.94) Hz. CRT TV requires a 144 degree shutter.

Shooting non-HMI-safe frame rates with HMI's requires changing the shutter angle.

Fast shutter effects require... a faster shutter.

Speed ramping without an iris pull requires a change in shutter angle (but that's with a more sophisticated camera anyway).

None of these things are really that big a deal most of the time, and the "work around" depends on the situation. You might rent a different camera body; change the flicker of the item in question, avoid it altogether, live with the effect, etc...
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