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Hmi Safe Shutter?


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#1 Danish Puthan Valiyandi

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Posted 26 May 2005 - 04:33 AM

I'll be shooting a Musicvideo- using the 16mm Arri SR-3.
Giving easily the possibility to change the Shutterangle- the director wants
me to shoot with an 45° angle.
Anyway- being honest I never shot 45° before :)

Using the rule- Hmi lamps at 50Hz- it wouldn't be a problem shooting
with 45° and 25 fps(?)

Anyway.. I'll be also using Kinoflos... will that be a problem?

Thanks in advance for your answers :rolleyes:

Greetings,
Dan

Edited by Danp, 26 May 2005 - 04:35 AM.

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#2 David Mullen ASC

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Posted 26 May 2005 - 11:27 AM

The problem with a 45 degree shutter is not FLICKER but EXPOSURE.

Under ordinary AC lights cycling at 50 or 60 hz, with such a short shutter speed, you may catch the pulsing light at the bottom, middle, or the top of the sine wave each time you roll. So you won't get frame-to-frame exposure fluctuations (flicker) but one take may be dimmer than another. With a normal shutter angle, you usually catch two to two and a half pulses per frame. But with a 45 degree angle, you are only catching part of a single pulse each time.

However, with high-frequency AC lamps like Kinos or an HMI on flicker-free mode, it should not be a problem.
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#3 Danish Puthan Valiyandi

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Posted 26 May 2005 - 01:45 PM

Thanks David, I appreciate your answer.
That's everything I wanted to know :)


Greetings,
Dan
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#4 Bob Hayes

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Posted 27 May 2005 - 03:57 AM

I've been shooting in Thailand at 50 cycle hmi in flicker free mode at all speeds and 45 degree shutter no problem. Kinos had no problem either.
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#5 Bob Hayes

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Posted 27 May 2005 - 03:59 AM

David:

Are so saying that regualr Tungsten may have exposure differences take to take with a 45 degree shutter?

Bob
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#6 David Mullen ASC

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Posted 27 May 2005 - 10:01 AM

David:

Are so saying that regualr Tungsten may have exposure differences take to take with a 45 degree shutter?

Bob

<{POST_SNAPBACK}>


No, just AC discharge type lamps that pulse at 50 or 60 hz.
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