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M18 flicker in "flicker-free" mode


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#1 Elliott Balsley

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Posted 20 February 2012 - 03:24 AM

I was shooting a short film last weekend on a RED One (MX). Project was at 23.98fps with a 180° shutter. Everything was going swell until I changed the shutter to 45° for one shot. I got a rolling band of warmish color on the LCD, and it shows in the footage too. In a hurry, we didn't have time for empirical tests, but we fixed it by changing the shutter to 86° (if I remember correctly). The only light in the scene was daylight through the window, an M18 HMI set to flicker-free mode, and some very dim incandescent china balls overhead. I had a 1/4 black pro mist on the lens.
I'm very confused, as I thought flicker-free mode on an electronic ballast was supposed to allow shooting at all frame rates and shutter speed combinations. How do you explain this? Should I tell the rental house their light is broken?
I will post a clip soon, when I get it back from the editor.
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#2 Elliott Balsley

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Posted 20 February 2012 - 05:16 AM

Here is a link to the footage:
http://dl.dropbox.co...0210GP full.mov
This was transcoded to 1920x1080 H.264 with full debayer.
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#3 Matthew Parnell

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Posted 26 February 2012 - 07:09 AM

I wouldn't put it past the china balls to have some involvement in the flicker. I've seen tungsten flicker like this on the red before(long story) abeit almost to the point of it only being visible on the waveform.

By all rights the M18 should have been right provided it was definitely in flicker free mode. I'd let the rental house know however. They should be able to get their tech to run a scope over the output side of the ballast just to check it out for their own sake.
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