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Lighting for Flourescents and Mercury Vapor


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#1 Jonathan Bryant

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Posted 24 August 2005 - 06:46 PM

I have to film a few scenes in a bio lab tommorow. I will probably only have time to add supplemental lighting to scenes that have Flourescents ant Mercury Vapors.

One will be a clean room (Just like the white room that you see the guys in white suits manufacturing Intel chips in) I have been told it has some sort of weird warm light. Since I can't enter I will be stuck outside shooting through some window. Not sure what I will do about color balance, probably will take a LCD monitor and adjust preset color balance on my DSR500.

Another scene will be a fermenting room. Probably to large to light solely with my lights. And probably either flourescents or mercury vapor lights.

What do you guys think since they want me to work fast, and only add light where its needed?

Should I just add a junior light with the correct color balance gel to key closeups to take away the flat look?

I have a nice magenta gel that I could use on maybe the back light or as a kicker.

Any thoughts woud be greatly appreciated!
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#2 Bob Hayes

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Posted 24 August 2005 - 07:00 PM

Magenta is the wrong direction to go. The lights you are shooting under will probably require full green correction. The Cooler colors will probably require full green and half blue. The very orange looking lights, I think they are Sodium Vapor, will require full green and ¼ or ½ CTO one your lights. The lights you add will look pretty weird to the eye but should balance out well.
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#3 Jonathan Bryant

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Posted 24 August 2005 - 08:19 PM

Magenta is the wrong direction to go.  The lights you are shooting under will probably require full green correction. The Cooler colors will probably require full green and half blue.  The very orange looking lights, I think they are Sodium Vapor, will require full green and ¼ or ½ CTO one your lights.  The lights you add will look pretty weird to the eye but should balance out well.

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The magenta would be for a color effect. Since this will be a lab I think that would add to the techy look.

What color temp are sodium vapor? I have a full green and a full CTO gel but I don't have 1/4 or 1/2 gels. I guess I need to get some.
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#4 Eric Brown

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Posted 24 August 2005 - 09:41 PM

The magenta would be for a color effect. Since this will be a lab I think that would add to the techy look.

What color temp are sodium vapor? I have a full green and a full CTO gel but I don't have 1/4 or 1/2 gels. I guess I need to get some.

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I'm paraphrasing/summarizing Blain Brown's explanation of these types of light sources.
More or less.
Sodium vapor, Mercury Vapor and fluourescents are discharge sources and have discontinuous spectra, meaning they do not have a continuous spectrum source and therefore are not assigned a true color temperature.
For more info you might want to check out his book "Cinematography: theory and practice." A must read for anyone serious about understanding lighting for film and video.
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#5 Mark Austin

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Posted 29 August 2005 - 04:06 AM

Hello,
I'm shooting a Spec Commercial on a Stadium Track at night. The track is lit by rich orange lights, similar to street lamps, so I'm guessing Sodium Vapor. I'm trying to match my HMI's to the stadium lights so I can shift to whole thing to the bluish range. Anybody have a solution to match HMI's to Sodium Vapors. Thanks!

Mark
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#6 Michael Nash

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Posted 29 August 2005 - 11:47 AM

Anybody have a solution to match HMI's to Sodium Vapors.

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Oof! That's what you might call going 'round your a$$ to get to your elbow. ;)

You've got a long way to go to get blue HMI's to match pink-orange sodium vapor. You're really better off starting with tungsten lights, and warming them up from there. I've been able to get tungsten to match sodium very convincingly with a combination of bastard amber and 1/4 CTO. Aim for about 3/4 density; no more than the equivalent of full CTO.

If you must use HMI's, you'll have to use full CTO first to get them up to tungsten color temp, than warm it up as you would tungsten. The problem is that when you start layering that much gel on a discharge light (which HMI's are), you're bound to get all kinds of funky MIRED shifts where the color doesn't behave quite as it's supposed to.

But unfortunately sodium vapor is a discontinuous spectrum, which means if you get all your lights to match perfectly you'll never be able to restore a "normal" looking balance in post, if that's your intention. You're probably better off filling in with warmed-up tungsten light to capture the most color, and then bluing that up a little in post if the look is too warm for you.
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#7 Chris Cooke

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Posted 29 August 2005 - 09:03 PM

Oof! That's what you might call going 'round your a$$ to get to your elbow. ;)

You've got a long way to go to get blue HMI's to match pink-orange sodium vapor. You're really better off starting with tungsten lights, and warming them up from there. I've been able to get tungsten to match sodium very convincingly with a combination of bastard amber and 1/4 CTO. Aim for about 3/4 density; no more than the equivalent of full CTO.

If you must use HMI's, you'll have to use full CTO first to get them up to tungsten color temp, than warm it up as you would tungsten. The problem is that when you start layering that much gel on a discharge light (which HMI's are), you're bound to get all kinds of funky MIRED shifts where the color doesn't behave quite as it's supposed to.

But unfortunately sodium vapor is a discontinuous spectrum, which means if you get all your lights to match perfectly you'll never be able to restore a "normal" looking balance in post, if that's your intention. You're probably better off filling in with warmed-up tungsten light to capture the most color, and then bluing that up a little in post if the look is too warm for you.

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Very true Michael. I just finished a shoot that involved sodium vapor lights and I used them as a backlight. I got this redish orange color that looked kinda neat when white balanced to tungsten. It was actually more to the red end of the spectrum than I expected. Out of curiosity's sake, I also tried white balancing to the sodium vapors and used them as my key. That was a mistake. Skin tones went all wanky on me. HMI's are soooooooo far off sodium vapor lights though that you'll have to use a lot of gells to get anywhere close.
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#8 Michael Nash

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Posted 30 August 2005 - 05:14 PM

I got this redish orange color that looked kinda neat when white balanced to tungsten. It was actually more to the red end of the spectrum than I expected.

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That's inherent to video because of the way the camera captures and reproduces color. Video has a hard time seeing "in-between" or secondary colors and has to reconstruct them out of the available luminance from the neighboring colors. So sodium always comes out reddish on video, but not on film. You'll also notice that video cameras are practically incapable of reproducing purple; it always goes blue. Magentas yes, but not purple.

To get around this in some cases I've used the skin tone function to isolate the red, then shifted the hue toward green so that the lights appear more orange and natural. It's not pefect and can introduce color artifacts, but sometimes you don't want that harsh, ugly red in the scene if the material is supposed to appear more warm and pleasant. You can also control the color with RGB (aka white balance) or matrix controls, depending on the camera.
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#9 Paul Bruening

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Posted 04 September 2005 - 02:15 PM

Street and industrial lighting is a nightmare for low-budgers. Can you change angles to leave the sources out of the shot? If you can, then you can often wash out the effects of those lights by splashing your lights through the scene. Otherwise.... just claim you did it on purpose.
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