Jump to content


Photo

HMI + Alexa


  • Please log in to reply
4 replies to this topic

#1 Marie Davignon

Marie Davignon

    New

  • Basic Members
  • Pip
  • 9 posts
  • Cinematographer
  • Montreal, Quebec, Canada

Posted 16 June 2011 - 07:49 PM

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!
  • 0

#2 David Mullen ASC

David Mullen ASC
  • Sustaining Members
  • 16103 posts
  • Cinematographer
  • Los Angeles

Posted 16 June 2011 - 07:57 PM

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.
  • 0

#3 Marie Davignon

Marie Davignon

    New

  • Basic Members
  • Pip
  • 9 posts
  • Cinematographer
  • Montreal, Quebec, Canada

Posted 19 June 2011 - 03:20 PM

Thanks!
  • 0

#4 Phil Rhodes

Phil Rhodes
  • Sustaining Members
  • 9621 posts
  • Other

Posted 19 June 2011 - 05:09 PM

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

There appear to be no rules.

P
  • 0

#5 Gregory Middleton

Gregory Middleton
  • Basic Members
  • PipPip
  • 78 posts
  • Cinematographer
  • Vancouver BC

Posted 28 June 2011 - 06:03 PM

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!


  • 0


Zylight

CineTape

The Slider

Paralinx LLC

Rig Wheels Passport

K5600 Lighting

NIBL

Abel Cine

Visual Products

Aerial Filmworks

rebotnix Technologies

Cinelicious

Ritter Battery

Media Blackout - Custom Cables and AKS

Pro 8mm

Cadrage Directors Viewfinder

Robert Starling

Glidecam

CineLab

Visual Products

The Slider

Cadrage Directors Viewfinder

Glidecam

Robert Starling

Abel Cine

K5600 Lighting

CineLab

CineTape

Media Blackout - Custom Cables and AKS

Zylight

Pro 8mm

Rig Wheels Passport

NIBL

Ritter Battery

Paralinx LLC

rebotnix Technologies

Aerial Filmworks

Cinelicious