flicker free help

[Geoff Haas]

I am wondering where (online) I can find the film safe speeds for filmming with "non flicker free" ballast's? Thanks for any advice.

[Mike Panczenko]

This website gives you safe speeds for HMIs at any shutter angle, I believe:

http://www.cely.com/digital/flickerfree.html

 

And this page gives you an equation to calculate for any shutter angle:

http://www.psps.com/pages_frames/tips/m_tip6.htm

[Michael Nash]

It's a pretty simple formula called the "twice the frequency rule." Any number that divides evenly into twice the frequency of the power supply is an HMI-safe frame rate for any shutter angle.

 

That means in the US at 60Hz., the whole numbers that divide evenly into 120 (twice 60) are:

1, 2, 3, 4, 5, 6, 8, 10, 12, 15, 20, 24, 30, 40, 60, 120.

 

Not that hard to memorize after a while, and also easy to figure in your head if you remember the rule.

[Laurent Andrieux]

...assuming you shoot at 180 ° shutter angle...