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Green Color Temperature Lamps?


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#1 Nick Centera

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Posted 04 November 2010 - 06:31 PM

Hey, I was wondering what are the usual lamps that have more of a green balance to them? Obviously flos have the green, but what other lamps unless they are all flo based. I have seen some street lamps that are green, which are those? Also, can you really trust the kelvin reading on store bought flos? If it is 2900k, will it still have some green it as well as being warm? Thank you!

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#2 John Sprung

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Posted 04 November 2010 - 08:17 PM

The green in both flourescents and some street lamps comes from mercury vapor. Other street lamps use sodium vapor, which is orange instead. Indeed, you can't trust the so-called color temperature on consumer flourescents. The green pulls them away from the actual color temp curve, which runs from reddish to blueish. Green/magenta is "sideways" to color temperature.

If you want to work with flourescents, the answer is:

http://www.kinoflo.com/





-- J.S.
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#3 Nick Centera

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Posted 04 November 2010 - 08:27 PM

Alright cool. So are mercury vapor lamps usually practicals in a scene? I seemed to notice them a lot in no country for old men a lot as just an example. Kinos are great, are their kelvins true? I've heard they have a very slight green to them.
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#4 Adrian Sierkowski

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Posted 04 November 2010 - 10:39 PM

All floros has some greenish, but Kinos have very very little. When it comes to Floro and other vapor type lights (minus sodium as I know don't if they have this) you look at the CRI, or Color Rendering Index. It runs up to 100, and for "film work," you want a light with a CRI of 90+ this will mitigate the "green spike," inherent in Floro tubes (though I say they always have it, and don't like them not HMIs as much as I do Tungsten units).
You'll generally encounter the mercury type lights on night EXTs and in some industrial locations, at which point many people choose to keep them as practicals in the scene and gel their own units to match.
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#5 Nick Centera

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Posted 04 November 2010 - 10:46 PM

So is there a big difference between the green on a store bought flo compared to more "industrial" mercury vapor lamps you encounter outdoors?
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#6 John Sprung

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Posted 05 November 2010 - 02:45 PM

So is there a big difference between the green on a store bought flo compared to more "industrial" mercury vapor lamps you encounter outdoors?


The actual mercury green spike at 546.1 nanometers is the same, but they look very different because the flourescent produces most of its light by using a mixture of phosphors to convert UV into visible, while the industrial and street lighting mercury vapors don't.




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#7 JD Hartman

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Posted 06 November 2010 - 01:29 PM

In addition to Mercury vapor, MH and HP Sodium streetlights, were now seeing induction florescent lights appear. That is at least in the NJ area.

Edited by JD Hartman, 06 November 2010 - 01:30 PM.

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#8 John Sprung

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Posted 06 November 2010 - 10:40 PM

Interesting -- how do induction flourescents work? Do they contain mercury, or do they generate UV or excite the phosphors in some other way?




-- J.S.
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#9 Michael E Brown

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Posted 07 November 2010 - 10:05 AM

Interesting -- how do induction flourescents work? Do they contain mercury, or do they generate UV or excite the phosphors in some other way?

-- J.S.


They still have mercury. They are very similar to what we consider normal flos, excited mercury creates UV and the phosphors convert to visible light. They are also known as electrodeless lamps - it basically has an electromagnet wrapped around the tube. Life span can be up to 100,000 hrs, and with very little lumen depreciation since most depreciation is a result of the electrodes deteriorating in normal flos. They have been around for a while (invented by Tesla, commercial lamps around since 1990s), there are probably some downsides that make it inappropriate for mass use (at least so far).

There is also another type of electrodeless lamp that I have found very interesting, the plamsa lamp (HEP). These lamps excite a plasma in a gas tube by focusing RF waves. These lamps have a very tiny light source, so can pack a considerable amount of lumens into a small lamp. Life span is supposed to be around 20,000 hrs, considerably more than a metal halide. They have not really caught on, so as with flos above there are probably more downside than is immediately obvious.

Edited by Michael E Brown, 07 November 2010 - 10:06 AM.

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#10 JD Hartman

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Posted 07 November 2010 - 02:00 PM

PSE&G has had an ongoing campaign of replacing the HID streetlights with induction flo's in NJ for some time. Have not shot in any location lit by them yet.
Similar to: http://www.everlastl...HUS-EC-70W.html
Theory: http://en.wikipedia....ctrodeless_lamp
Another ongoing trend, 7-Eleven is changing all its exterior lighting to LEDs. LED platform lighting also exists at some of the newer NJ Transit stations.

Edited by JD Hartman, 07 November 2010 - 02:02 PM.

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#11 John Sprung

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Posted 07 November 2010 - 05:51 PM

There is also another type of electrodeless lamp that I have found very interesting, the plamsa lamp (HEP).


Sounds like this:

http://www.luxim.com/

The downside seems to be that the support electronics are only economically practical for high output applications, equivalent to thousands of watts of tungsten.

Here are some LED sources:

http://www.ledtronic...eet_lights.aspx





-- J.S.
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#12 Michael E Brown

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Posted 07 November 2010 - 06:40 PM

Sounds like this:

http://www.luxim.com/


Ya, they were one of the first to bring it to market in a commercial fixture that I saw - a Robe brand moving head. I think their competition Ceravision has won some patent suits against them, possibly putting them in a tight spot. Ceravision appears to be interested more in industrial lighting than much else.
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