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Matching tungsten to cloudy exterior

David Calson

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5600K is reckoned to be a mixture of sun and skylight. Tungsten with a full CTB will still be a bit warm in cloudy daylight, which is a bit bluer, so it might need 1½ or double CTB if you actually want full correction.



Talk about impractical. Nothing is more impractical than gelling a tungsten light to balance it to overcast daylight


Balancing tungsten to 5000K with full CTB cuts the output of the light by 70%, which means that a 1000W 3200K light becomes a 300W 5000K light when you put Full CTB on it. To put double CTB on to balance to the much cooler overcast light will cut the output of a 1000W 3200K light to a 160W light. In situations like this it would be better to use 5500K light sources, like an HMI, to start with. A HMI will give you considerably more lumens/watt than a color corrected Tungsten 1k, and use up a lot less power.


When you are starting out it is easy to underestimate how bright daylight is even on an overcast day. Since the sun puts out something like 10’000 foot candles, even on an overcast day a large HMI is needed. Big shows that I have worked on use a 12k Par and diffuse it heavily to match the shadowless light of an overcast day. Where you probably can’t afford a big HMI and the big generator to operate it, your best bet would be a 4k Par through a light diffusion since they can be run on a modified Honda EU7000 generator. To record dialogue without picking up the sound of the generator, you should run the generator out of the back of a van or truck. To avoid line loss over the long cable run to the generator use a Transformer/Distro on set to boost the voltage to compensate for the drop of voltage you will get over the long cable run.


If you have any questions about using transformers with generators, I would suggest you read an article I wrote on the use of portable generators in motion picture production. Harry Box, author of “The Set Lighting Technician’s Handbook” has cited my article in the just released Fourth Edition of the handbook.





If you haven't yet read the article, or looked at it in a while, it is worth reading. I have greatly expanded it to be the definitive resource on portable power generation for motion picture production. Of the article Harry Box states:


"Great work!... this is the kind of thing I think very few technician's ever get to see, and as a result many people have absolutely no idea why things stop working."

"Following the prescriptions contained in this article enables the operation of bigger lights, or more smaller lights, on portable generators than has ever been possible before."


Use this link for my news letter article on the use of portable gas generators in motion picture production.


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




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