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I have been researching and speaking with Engineers for days about how to build a lighting rig that does not band 96 or 120 frames per second. The GH4, for example, is a camera that requires more light than usual, so I have to have at least 500W power to provide efficient light. Where are these powerful high CRI halogens? I am searching for the bulb specifically. I can build a ballast with a capacitor to offset the peaks in order to avoid banding.

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I have been researching and speaking with Engineers for days about how to build a lighting rig that does not band 96 or 120 frames per second. The GH4, for example, is a camera that requires more light than usual, so I have to have at least 500W power to provide efficient light. Where are these powerful high CRI halogens? I am searching for the bulb specifically. I can build a ballast with a capacitor to offset the peaks in order to avoid banding.

 

Any tungsten halogen bulb can operate DC as well as AC. The trick is to provide it with 120V DC. The traditional approach to powering tungsten lights with DC on stages was to wire ten 12V deep cycle marine batteries in series. But, in response to a DP’s recent posting on the CML, for some way to power a chandelier flicker-free for a high-speed commercial shoot (pictured below), I built him a 120V AC to 120V DC power converter so that he could power the chandelier and other practicals flicker free at high speeds. He shot with it several weeks ago and reported that it “performed beautifully” and at “2,000fps was rock solid.”

CPS_Cultivate_Studio_HS_Prod.jpg

 

The one I built for him could handle up to a 1000W tungsten load, but I have since scaled up the design to handle a Jr. with CXZ lamp. The larger converter (pictured here) will accept input AC voltages from 90-140V, and 190 – 250V and put out a constant 120V DC. It can operate at both 50 and 60 Hz. It also has a series LED display to indicate the total load put on it between multiple tungsten Fresnels and incandescent practicals.

CPS_30A_Power_Converter_SM.jpg

 

And, as you can see in the picture above, it is a lot smaller and lighter and more easily concealed on a set than ten 12V deep cycle marine batteries, wired in series, which has been the traditional approach to powering tungsten lights with DC on stages.

 

Guy Holt, Gaffer, ScreenLight & Grip, Lighting and Grip Rental & Sales in Boston.

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I shot some very quick tests at 180fps on an FS7 the other day - under ceramic metal halide light, and surprisingly, it was absolutely fine. This is counterintuitive, because CMH usually can't be driven at high frequency, but it's absolutely spot on.

 

This is the sort of technology that's sold by people like Cool Lights in their ceramic metal halide fresnel. The effect may be somewhat ballast-dependent, but it's worth testing.

 

P

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Guy Holt - beautifully constructed, elegant solution. What is the total load the new one will accept ?

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Guy Holt - beautifully constructed, elegant solution. What is the total load the new one will accept ?

 

As described above, the capacity is 1500W.

 

Guy Holt, Gaffer

ScreenLight & Grip

Lighting Rental and Sales in Boston

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