Avoiding flourescent flicker all together

Brandon Whiteside · April 7, 2009

I started by doing a search on the topic "Flourescent flicker" and came across nothing useful. This weekend i am shooting 24p with an xl2 in a classroom, using the built in flourescents. What are the chances we experience problems?

Thanks so much!

JD Hartman · April 7, 2009

Here: http://www.cinematography.com/index.php?sh...&hl=flicker If the fixtures have electronic ballasts, you'll probably be fine. Shoot some test footage and see what results.

You profile indicates "Student". What did your instructors advise?

Steve McBride · April 8, 2009

Make sure your shutter speed stays at 1/60 of a second. The fluros run at 60hz which means 60 cycles a second, so when you're frame rate is 1/60 of a second you are getting 1 full cycle in the lights every 1/60th of a second which makes for 60 full cycles in a second. That basically means that the lights will look fine.

I may be completely off, or just slightly off here. Wait for someone else to confirm or deny what I have said before you trust it :) .

I also just realized that that really didn't make any sense, so hopefully someone can come through and help me out also. I'll look into it again because I know I read this not too long ago and if I find it I'll reply back.

Edited April 8, 2009 by Steve McBride

Brandon Whiteside · April 8, 2009

I will be shooting 24p at 1/48th. What about that?

Adrian Sierkowski · April 8, 2009

You should be fine 24 @1/48s. It's a safe speed.

Brandon Whiteside · April 8, 2009

Yay!

Steve McBride · April 8, 2009

Guess I was probably wrong. I need to find that article...

Adrian Sierkowski · April 9, 2009

No, you're also right that you're ok at 1/60th of a second. It's also a safe speed.

http://www.panavision.com.au/Information/Flickerfree60Hz.htm

"Any Shutter Angle" for those interested, would also be any shutter speed.

Peter Apt · April 12, 2009

If I was shooting with a Sony EX3 under 50hz lights (Australia) overcranked at 32fps (or 31) with a 1/50 shutter will I get flicker? I am going to put the overcranked footage into a 25fps timeline. Thanks

Adrian Sierkowski · April 12, 2009

You'd be risking flicker:

http://www.panavision.com.au/Information/Flickerfree50Hz.htm

Peter Apt · April 12, 2009

You'd be risking flicker:
http://www.panavision.com.au/Information/Flickerfree50Hz.htm

Thanks Adrian, I will have to test it... I was under the impression with a cmos as opposed to film, that the shutter speed was the determining factor for flicker rather than framerate.

Cheers

Adrian Sierkowski · April 12, 2009

It's true, but generally frame rate and shutter speed are linked together. it depends on your own camera, of course. If you wanted it to react as film does you'd change the shutter speed with the frame rate.. but you don't necessarily need to.

In theory, you could keep it at 1/50th to a point (50 fps perhaps) wherein you can't fit anymore frames for that rate (does that make sense).

For ~34 fps.. you might be Ok, but personally w/o testing I'd not bank on it. Thankfully all you need is a floro bulb to give it a try (though of course, the ballasts in your location will behave differently than the ballast you test, in theory).

Good Luck!