Cyc Lighting for High Speed

[john wenman]

What’s a cost effective way of lighting a 15’ high cyc for 500FPS? Preferably from a grid and not off the floor  

I’m still using old IRIS 1s but I’m worried about flicker. 

Edited February 27, 2021 by john wenman

[Jay Young]

Couple of 10ks ought to be effective. 

[Stephen Sanchez]

You're worried about flicker with tungsten? I've never shot that high FPS in tungsten light before. Are you able to run an FPS test with some tungsten light on a wall somewhere?

As for the cyc level. Given that it's white, it doesn't take too much power to make it hot fire. I've set 9 of those IRIS cyc lights for a 40ft cyc with 14ft height and 250 diff in each. I think I had set the IRE of the cyc to 80, which brought the iris to f16. At 1250 ISO, 30fps. I'll have to double check if that's right.

[Stephen Sanchez]

Okay so for a 9k 40ft cyc (1k IRIS every 4 feet), the wall spot-metered for middle gray at f22.

In-camera, 30p at 1250 ISO. Monitoring on a Rec709 LUT, this read as: f8 at 80 IRE, f5.6 at 90 IRE, f4 at 100 IRE. It seems that one stop on the FS7 is 10 IRE.

500fps is around 4.2 stops more than 24/30 fps. If my math is correct, if you want to be at f4 and a 100 IRE cyc, the 4 stops needed for slow-mo would be 144,000 watts, or x14 10ks. Oh my...

[Stephen Sanchez]

Of course that's for the whole 40' run.

[Matthew Parnell]

1ks, especially the double ended lamps in Cyc lights are pretty much guaranteed to flicker at 500fps. 
 

The general rule for lighting high speed with tungsten is to go 5k filaments and above. 5k skypans would be a great option if you can get your hands on them, or likewise 5k fresnels with some diff would be good. 
 

You could also go HMI with 1000hz ballasts. Arri X lights would be an ideal quick solution for the cyc.

LED or Kino might be an option, but I can’t see you affordably getting the coverage and level you need. 

[Guy Holt]

12 hours ago, Matthew Parnell said:

1ks, especially the double ended lamps in Cyc lights are pretty much guaranteed to flicker at 500fps. 

You can use the 1kW Iris lights without flicker.  The reason that you get flicker from small filament bulbs (<5kW) is that at high speeds the camera will capture the changing intensity of the light output of the bulb as it rises and falls as the voltage waveform rises and falls.  If you use three 1kW Iris where you would normally use one, and put each fixture on a separate phase of the power service, the light output between the three fixtures will be constant as each compensates for the  drop in intensity of the other.  

Guy Holt, Gaffer, ScreenLight & Grip, Lighting Rentals & Sales in Boston

[Matthew Parnell]

4 hours ago, Guy Holt said:

You can use the 1kW Iris lights without flicker.  The reason that you get flicker from small filament bulbs (<5kW) is that at high speeds the camera will capture the changing intensity of the light output of the bulb as it rises and falls as the voltage waveform rises and falls.  If you use three 1kW Iris where you would normally use one, and put each fixture on a separate phase of the power service, the light output between the three fixtures will be constant as each compensates for the  drop in intensity of the other.  

Guy Holt, Gaffer, ScreenLight & Grip, Lighting Rentals & Sales in Boston

I understand the theory, and have had it work successfully many times before, but unfortunately I’ve also had image flutter at as low as 200fps using phase distribution both with Cyc strips and Spacelights.
 

Even using phase spreading, the individual sources are still flickering and the light being projected does move around at those high frame rates as a result. Sometimes you do get away with it, sometimes you don’t. Having seen it go wrong, unless you can afford to test it, compromise to a lower frame rate on the fly, or have the manpower and equipment to re-light it, it’s a risk that I’d prefer not to take.