what's real the deal with correcting flos?

peter kantor · August 21, 2006

I'm talking about tubes that read green (4300K), not Kinos or Optima 32's or Chroma 50's.

Is it sometimes a two step process or what? For example, minus green will bring the color temperture to 3200K.. making a match with tungsten lights. But if the goal was to get them to match HMI's, would I still use minus green in combination to CTB? Or simply CTB alone? It seems that too many footcandles would be lost with more than one gel.

This is assuming there was no color temperature meter on set.

Michael Collier · August 21, 2006

Well decide your goal color temp and choose the tubes you are using. Some lamps need CTB, others do not. If you look at Roscors website they have a chart of mired shift that basicly outlines it all for you. If your on a delux cool white you need a certain combination of filters (this is especially good because not every lamp needs a full stop of neg-green.)

You also have other options if you dont want to gell every light with CTB and neg green. For example you could add plus green to all the HMIs to bring the green-spike in every lamp. Then add a neg-green filter over the lense (I believe they are R40 filters, but I would check the roscor lit. or kodak lit for a solid answer) Your still loosing the same amount of light, but you will save time and money by not having to gell the 200 overhead floro units and only gelling the fixtures you provide (fixures that can stand a little bit of light loss.

Be sure to check every lamp for type, all tubes are not equal. some are ballanced to 5600k, some to 3200k. Sometimes in a building you will see several different types in the same type of fixture.

Hal Smith · August 21, 2006

Well decide your goal color temp and choose the tubes you are using. Some lamps need CTB, others do not. If you look at Roscors website they have a chart of mired

Here's a handy link at Rosco's website. It gets conversion for different types of fluorescents down to a recipe. For instance: Warm White Flo to Daylight: 1/2 CTB + Minus Green

http://www.rosco.com/includes/technotes/fi...terFacts_05.pdf

Kristy Tully · September 1, 2006

yes it's a two part process. Minus green removes the green- I use 1/2 minus green instead of full. I've found it looks better on film and takes less light away. Then you need CTO to take 4300 down to 3200. I's use 1/2 again.

Sounds like warm deluxe bulbs. So to match to HMI's you'd need as already said, CTB and minus green. I personally under correct fluorescents a bit. So in this case I'd use 1/4 CTB and 1/2 minus green. Partly because I always find it looks better later, and also gives you a little more light on set.