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Practicals for high speed


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#1 Kendal Miller

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Posted 16 August 2013 - 08:02 PM

I have a phantom flex shoot coming up and I have solved all of the lighting issues with one major exception. I have a handful of small practical lamps that appear in frame, and I cannot for the life of me think of a good way lamp them? Any ideas or thoughts??


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#2 Stuart Brereton

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Posted 16 August 2013 - 09:06 PM

Small filament tungsten bulbs, like those commonly found in practicals, are likely to flicker on AC power. Could you switch them out for low voltage DC equivalents and run them from a Leisure battery? Maybe use MR16 globes and rig some sort of reflector inside the lampshades to spread the beam more evenly?


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#3 Guy Holt

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Posted 17 August 2013 - 01:09 PM

Small filament tungsten bulbs, like those commonly found in practicals, are likely to flicker on AC power. Could you switch them out for low voltage DC equivalents and run them from a Leisure battery? Maybe use MR16 globes and rig some sort of reflector inside the lampshades to spread the beam more evenly?

 

 

I have no practical experience (excuse the pun) using CFLs  in high speed cinematography to say if they will flicker, but I found a website called lucidmovement.com that suggests CFLs will sufficiently flicker-free up to a 1000fps to be used in practicals. Lucid Movement describes itself as a video blog that was created to “display the wonder of the world through the lens of a high-speed / slow motion camera.” In addition to displaying highspeed videos, this site also acts as a video reference for artists and researchers by including information on how the shot was created - including specific camera settings and lighting instruments used. According to this information, most of the high speed clips on the sight are shot between 1000 and 2000 FPS with a  Photron Ultima APX and, in fact, use 16 x 30Watt CFL Banks (the Fotodiox Cool Light c-1600) for lighting. 

 

 

If you look at the clips, there is a slight flicker at 2000FPS, that is appreciably less, but still present at 1000FPS. There is also an actual clip of a 16 x 30Watt CFL bank turning on at 2000FPS (http://www.lucidmovement.com) Where the bulbs themselves do not appear to flicker in this clip, even at 2000FPS,  and the objects lit by the bulbs barely flicker at 1000FPS, suggests that the slight flicker of CFLs may not be noticeable when used in practicals at 1000FPS.

 

What might make CFL bulbs  sufficiently flicker-free is that contain tiny electronic ballasts that apply high frequency output, around 40 kHz or higher, to the lamp tube. At those frequencies the period of time between the off and on pulse of each cycle is so short that the illuminating phosphors in the lamp tube may not decay in light output enough to cause a flicker. Like the  'thermal inertia' of tungsten bulbs - metal glowing white hot - that keeps them emitting light for a short time after the power drops off, the phosphors continue to glow after the power drops off as it switches at high frequency making them possibly flicker free. Lowel  in fact states on their website that “our 80 Watt daylight fluorescent lamps (provide) high output with accurate color. Its high frequency ballast is designed for flicker-free hi-res digital still, video, and slow-motion cinema use.” 

 

Guy Holt, Gaffer, ScreenLight & Grip, Boston

 

 

 

 


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#4 Kendal Miller

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Posted 19 August 2013 - 03:02 PM

Guy,

Thanks for the info. I like the option of CFLs for this application alot.


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