4 replies to this topic

[Marie Davignon]

I have an important question :

Do I need to use flicker free HMI ballasts when shooting with the Alexa at 24 fps? 23,97?
Does it work like the RED, with a rolling shutter that can make some lines moving through the frame?

Thanks!

[David Mullen ASC]

I haven't had problems with older HMI's on either the Red or Alexa. Yes, the Alexa has CMOS sensor with a rolling shutter.

At 23.98 fps, you are on the edge of flicker but usually it's not noticeable unless you look at a waveform monitor.

[Marie Davignon]

Thanks!

[Phil Rhodes]

I have seen a 60Hz HMI flicker on a 7D at 1/60 shutter.

There appear to be no rules.

P

[Gregory Middleton]

Its always safer to shoot flicker free. You should be able to see any issues on the waveform however. Sometimes it will only show up from 1 light or at a particular angle depending on conditions as a very slow pulsing density shift.
Flicker free will make sure however of no issues at 23.98
Beware fluorescents in locations with magnetic ballasts however.

I have an important question :

Do I need to use flicker free HMI ballasts when shooting with the Alexa at 24 fps? 23,97?
Does it work like the RED, with a rolling shutter that can make some lines moving through the frame?

Thanks!