Using HMIs for High Speed Photography

[M Joel W]

I'm shooting a short video on the ts3cine. The location has a ton of natural light and it's a day interior. I'm scouting the location for light levels under various lighting conditions (overcast, full sun) to make sure we have the stop for high speed and that the sun will be out long enough, etc.

 

We're shooting at 750fps/f2.8/ISO800 and of course stopping down as need be if there is more light than is necessary. I want to light primarily with natural light as the space is too big to light with HMIs but we have the option of bringing in whatever HMIs we can drive off an unmodified 6500 EU for fill. We also have two fat men kinoflos for fill, both with daylight bulbs of course.

 

I'm working out my ratios and whatnot on my own but what I am worried about is

 

FLICKER!!!!

 

Which HMIs are appropriate for 750fps? I fear electronic ballast HMIs still won't be fast enough due to subtle flicker and arc wavering. My top choice is the M18, as I think I can run that and two four banks without blowing the gennie up, and I need to be conservative since it's the old ballasts that aren't power factor corrected or whatnot... But I am afraid this will flicker terribly.

 

Anyone have any advice? Any experience using HMIs for high speed? Again 750fps (1/1500 shutter) and an M18 is the current plan.

[Guy Holt]

Anyone have any advice? Any experience using HMIs for high speed?.... what I am worried about is FLICKER!!!! Which HMIs are appropriate for 750fps? I fear electronic ballast HMIs still won't be fast enough due to subtle flicker and arc wavering...

 

With the new Arri 1000Hz High Speed ballasts you will be able to achieve flicker free images at frame rates of 500 - 1000 fps and in many cases beyond. This new technology supplies the lamp with a greatly raised 1000Hz square wave current, allowing for high speed cinematography with HMIs for commercials, sports, industrial applications, automotive component testing, ballistics or material testing - even with a single HMI daylight source. 1000Hz High Speed Ballasts are available for all wattages from 125W – 4000W. Here’s a demonstration video from the Arri channel on youtube.

 

http://www.youtube.com/watch?v=OgiG_0DDBwQ

 

 

… we have the option of bringing in whatever HMIs we can drive off an unmodified 6500 EU for fill... My top choice is the M18, as I think I can run that and two four banks without blowing the gennie up….

 

If you want to use the M18 you have to make sure you have the high speed ballast (Arri model #L2.76626.KA) and not the standard ballast (Arri model #L2.76626.A). But, you can run a much larger HMI on a Honda EU6500is without blowing it up if you know how. For instance, with a Transformer/Distro you will be able to run the M40 with high speed ballast, along with the rest of your package, on a 7500W modified Honda EU6500is.

 

… I need to be conservative since it's the old ballasts that aren't power factor corrected or whatnot…

 

Rather than being conservative, be smart. Learn which HMIs ballasts are capable of what and how to operate them on portable generators. The poor Power Factor and flicker of HMIs have been vexing set electricians for years. For more information about the adverse effects these loads can have on generators and power distribution systems, and how to remedy them so that you can operate bigger, or more small, lights flicker free on portable generators or house power than has ever been possible before, join me in a workshop I am teaching on Feb. 16^th titled “Lighten Up: Doing More with Less without Compromise.” As part of the same workshop series, New England Studios, Talamas Broadcast, and Production Hub will be sponsoring a workshop on “Video Lighting Design”by L.D. Richard Cadena on Feb. 9th. Noted Focal Press Author, ETCP Trainer, and Founder of the Academy of Production Technology, Richard’s workshops are both lively and informative. Log onto bit.ly/nptwkshps for more workshop information and registration details.

 

 

Guy Holt, Gaffer, New England Studios, Lighting & Grip Rental in Massachusetts

Edited January 29, 2013 by Guy Holt

[Edward Lawrence Conley III]

Where are you located?

[M Joel W]

Boston. Renting the ts3cine.

 

Budget is very tight... nearest Arri FF ballast is in Detroit, or so says Arri.

 

Our current plan is to run the camera with a 360º shutter and dial down the frame rate until flicker is mitigated. Shutter will be 1/720sec, not that bad. Lights are an M40 (or M25) and daylight kinoflos. If we had more money we'd be shooting with a Phantom and proper lights, but we don't...

 

Any advice much appreciated. Director is okay with a little flicker since this is a horror montage cut to dubstep and there will be distress effects applied in post, too. Shutter on camera is global, too, so no artifacts beyond flicker.

Edited February 3, 2013 by M Joel W

[ChrisAdams]

I shot 300 fps on Epic on this video: https://vimeo.com/49073439 (skip to 1:37) and I lit it with just a 1.2k HMI with an electronic balast. Obviously we didn't have the budget for anything bigger or the high speed ballasts. But this shows you how much flicker you get at 300fps without that ballast. We also were at a 90 degree shutter I believe.

 

Also Denoiser was added in post which got rid of some of it.

 

Hope this helps.

[M Joel W]

Thanks... my hope is that by shooting with a 360º shutter (1/720) we shouldn't get as much flicker. We'll know soon enough. We have some plug ins to adjust in post. That looks okay... we would be happy with something similar.