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blue or green and tungsten or fluorescent?

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Nelson May
blue or green and tungsten or fluorescent?
on May 28, 2008 at 8:39:05 pm

'I am trying to do some keying in my humble garage studio. I have decided to work with daylight bulbs so I don't have to black out windows or wait until night.

I have a muslin green screen. Will that work best with daylight, or should I go blue.

I also want to use fluorescent lights. I have 300w and 600w frenels, but they blow too much heat.

Idea:? Can I use daylight fluorescent tube or shop light bulbs for my screen and can I use a combination of 150w fluorescent spirals for talent lighting?

Here is a diagram of what I want to do. I have been reading that the bulbs in Home Depot have the correct color index for daylight use. Is that correct. I would love to have Kino, but can't afford them.
/Users/nelsonmay/Desktop/green_screen_set.jpg
After shooting I was going to garbage matte my image and pull the key from there.
I am trying to upload a schematic, but can't find the upload button for this thread.



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Todd Terry
Re: blue or green and tungsten or fluorescent?
on May 28, 2008 at 8:57:36 pm

Well... some old schoolers (here and elsewhere) would probably say "Don't try that" (actually, not bad advice)... but...

It can be done, and I've probably done worse.

Just make sure that, like all key setups, that you light your key wall and your talent completely independently from each other. I know, it's the well-known Rule #1 in the Big Book of Keying, but it bears repeating.

Secondly, run a test or two to make sure that you don't have any flicker problems... since the fixtures from the big-box hardware stores aren't exactly flicker-free instruments like Kinos or electronic-ballast HMIs are. If so, it may be possible to overcome that if your camera as a variable shutter (film) or clear-scan mode (video).

But.... if you already have tungsten balanced instruments available, I personally would just pop 20 bucks for a roll of black Visqueen and cover the windows. That sure sounds a lot easier to me than buying a bunch of bulbs and rounding up shop fixtures that "kinda work."

But yes, it can be done....


T2

__________________________________
Todd Terry
Creative Director
Fantastic Plastic Entertainment, Inc.
fantasticplastic.com






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john sharaf
Re: blue or green and tungsten or fluorescent?
on May 28, 2008 at 9:02:47 pm

The color of the screen and the color of the lighting are two different things! Green is often chosen because there's blue in the foreground objects. Essentially you can use any color in the background that does not appear in the foreground.

As regards the color temperature of the lighting, you want to use the same (either daylight or tungsten) on both. This allows the camera to be white balanced properly and to make the color reproduction as accurate as possible.

Fluorescent shop lights do not produce accurate color rendering, so should be avoided. Proper photographic flo's (like Kino Flo) both have special color corrected tubes and ballasts that make the lights flicker twice as fast to create more light.

Of course you can do anything you want, just carefully observe your results and make the proper adjustments.

JS





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Michael Palmer
Re: blue or green and tungsten or fluorescent?
on May 30, 2008 at 3:02:11 pm

One other thing to remember is to keep your subject as far from the green screen as possible, as your green screen will reflect green back to your subject making it more difficult during the keying process. If you are just lighting the Green screen with the Flo's then just make sure and use the same brand and model. Color Temp and CRI levels aren't really important as long as you are just lighting the green screen.

If you are lighting people with these flo's then here is some information to keep in mind.
Fluorescent tubes come in a wide variety of not only color temperatures but various CRI ( Color Rendering Index) levels. You can look at the lettering on each tube that will tell you in most cases where the tube rates. A lot of tubes will have 70, 80 or 90 somewhere within the markings on the end of the tube. 70 CRI will have a higher green spike than 80 CRI or 90 CRI and they aren't really good for lighting people. I would suggest you find tubes that have as close to 5000 or 3000 kelvin as possible and has a 90 CRI rating for the best color spectrum representation. Look up Vita-Light
http://www.BulbTown.com/F14T12_DL_DAYLIGHT_FLUORESCENT_G13_BASE_p/9230.htm
Depending on the fixtures ballast type you should be able to find tubes that will light to the tubes capability or rating.
I found Philips T-8 tubes with 90 CRI in 3000k (TL-930) and 5000k (TL-950) kelvin temperatures that can be dimmed using the Mark X Philips electronic ballasts. Note the 9 is for 90 CRI and the 3 or 5 is for the kelvin degree. These tubes are beautiful and extremely color constant between tubes and tube sizes. The tubes you'll find at the big box stores should give you some indications of how they rate.

You may want to purchase some color corrective gel so you can add some blue to the tungsten units.
http://stagespot.com/gel.html?gclid=CM310Le9zpMCFSgtagodvQZChQ
I believe you should use anything and everything you have and learn what works for you. I hope this helps you.

Good Luck
Michael Palmer


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