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flicker, big space, many light sources


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#1 michael a brierley

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Posted 02 February 2009 - 04:33 PM

I am shooting a scene in the arrivals hall in Dubai Airport next week and I am unable to test the lighting in there due to security issues. There are many light sources in the place, ranging from LED's to fluorescents to metal halides - like most new airports, it's big and the director wants to see the place (that's why we are there, right?) I am shooting film @ 24 fps @ 172.8 degree shutter angle on 500 ASA, we will carry a smallish lighting package to supplement the existing ambience rather then try over power it. What are my options here? Does anyone have any idea if there is a safe shooting window to eliminate flicker? If I shoot @ 25 fps with a 180 degree shutter, would that eliminate the flicker issues? The power in Dubai runs @ 50 hertz - I am a DP not an electrician! Obviously flicker would be a disaster for the company (and me). Help, please...

Thanks and best,

Michael B
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#2 David Mullen ASC

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Posted 02 February 2009 - 04:38 PM

24 fps at 172.8 shutter angle and 25 fps at 180 degree shutter angle are the same shutter speed, 1/50th, so both are good for shooting 50 Hz lighting if your camera is at crystal-sync.
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#3 michael a brierley

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Posted 02 February 2009 - 05:02 PM

Thank you David. So one would suppose that in theory, all the lamps in the hall work on the same frequency - so no flicker?
Shooting on an ST and an LT, so both cameras are crystal sync.
I was out shooting tests of street lamps tonight and building sites and tracts of desert lit with sodium vapour lamps, will view the results tomorrow.
Thank goodness for Master Primes, Kodak 5219 and a Nikon D3.

Michael
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#4 Tim Fabrizio

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Posted 02 February 2009 - 05:14 PM

I have run into issues before with neon tube lights (the ones that you would see on a sign). I in shot a huge hotel lobby and behind the reception desk were this purple neon lights that ran from floor to ceiling. In the same shot were flourescents as well. Those I could dial out, as well as computer monitors. No matter what I did (shutter, speed, etc) I couldn't phase out the neon. It ended up looking cool and director loved it, got lucky.
David is correct though, at a 1/50th everything at 50hz should be fine.
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#5 John Sprung

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Posted 02 February 2009 - 06:07 PM

There are many light sources in the place, ranging from LED's to fluorescents to metal halides -


My concern would be the LED's. If they're in displays -- arrival/departure, advertising, etc. -- they may be running at their own refresh rate, not the power frequency. Flourescents in the old days ran at the mains frequency, more modern ones run at much higher frequencies, and are unlikely to be a flicker problem. In some places, I doubt Dubai is one of them, the mains frequency isn't all that accurate, either.

Given 50 Hz power and 24 fps, 172.8 degrees is the right answer. Bear in mind that your viewfinder doesn't show you the same shutter angle you're shooting with, so flicker in the finder isn't a clue as to what you'll get on film. On the old Eclairs, you could take the lens and magazine off, and run the motor while you looked straight through the aperture. That would show you exactly what kind of flicker or roll bar effects you'd get. With the Arricams, unfortunately, that wouldn't be practical.



-- J.S.
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