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#1 Jonathan Bel

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Posted 18 December 2010 - 10:55 PM

Whoa, maybe I'm just loosing my mind.

I seem to have forgotten what I've read and learned. I'm shooting 3200k tungsten stock. I want my lighting subject's face to have the fill light blue-ish and the key light normal. If I put a full CTB in front of fill and leave the key as is, how will this turn out? Should I gel the key as well, maybe with a 1/4 CTB to keep the "white" cast?

I just keep forgetting these things. CTB gels over lights on tungsten stock?? Conversion to 5500k? Someone refresh my weary mind.

Edited by Jonathan Bel, 18 December 2010 - 10:55 PM.

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#2 David Mullen ASC

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Posted 19 December 2010 - 12:58 AM

Whoa, maybe I'm just loosing my mind.

I seem to have forgotten what I've read and learned. I'm shooting 3200k tungsten stock. I want my lighting subject's face to have the fill light blue-ish and the key light normal. If I put a full CTB in front of fill and leave the key as is, how will this turn out? Should I gel the key as well, maybe with a 1/4 CTB to keep the "white" cast?

I just keep forgetting these things. CTB gels over lights on tungsten stock?? Conversion to 5500k? Someone refresh my weary mind.


If you want the key light to be "white", neutral, normal, i.e. 3200K for 3200K stock, then you wouldn't add blue gel to the tungsten key light.

If anything, to be completely precise about this, the "total" key light on the face is really the key + the fill, the fill adds to the intensity of the key. So a blue-ish fill would probably slightly raise (make cooler) the color temp of the key side of the face as well. But probably not enough to be worth adding some orange gel to the key to counteract the blue of the fill.
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#3 Jonathan Bel

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Posted 19 December 2010 - 08:48 AM

Thank you,

Slight dose of amnesia here. I was doing a lighting test on a mannequin, I wanted color on one side of the face but I got enchanted by the blue, forgot about color balancing.

Are their gels designed strictly for color effect, without temperature change? Sorry I don't have much experience with gels.




If you want the key light to be "white", neutral, normal, i.e. 3200K for 3200K stock, then you wouldn't add blue gel to the tungsten key light.

If anything, to be completely precise about this, the "total" key light on the face is really the key + the fill, the fill adds to the intensity of the key. So a blue-ish fill would probably slightly raise (make cooler) the color temp of the key side of the face as well. But probably not enough to be worth adding some orange gel to the key to counteract the blue of the fill.


Edited by Jonathan Bel, 19 December 2010 - 08:51 AM.

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#4 David Mullen ASC

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Posted 19 December 2010 - 11:50 AM

Thank you,

Slight dose of amnesia here. I was doing a lighting test on a mannequin, I wanted color on one side of the face but I got enchanted by the blue, forgot about color balancing.

Are their gels designed strictly for color effect, without temperature change? Sorry I don't have much experience with gels.


Of course there is a color temperature change, which is the point of CTO and CTB gels. I'm just saying that if you want a 3200K key light and your lamp is 3200K, then why do you think you need to add blue gel to it to get 3200K? It's already 3200K!

If anything, the light on the key side is the key plus the fill, and if your fill is blue, then the light on the key side is a mix of the 3200K key light and the blue fill light, so it probably ends up a bit over 3200K depending on how strong the fill is and whether it is frontal or coming from the opposite side as the key, etc. But it's probably not adding enough blue for you to want to add some CTO to the key to compensate.

Color temp gels have a MIRED shift listing on their color swatch, so you can calculate the shift in color temp. Of course, with a mix of two lights, you'd have to use a color temp meter to know what the final color temp ends up being, but since you were asking if you should put some CTB on the key light to keep it white (i.e. 3200K) if the fill has CTB on it, I'm saying no, if anything it would be the opposite.
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#5 Chris Burke

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Posted 19 December 2010 - 03:10 PM

Is it possible that the key light is more like 2700k and perhaps the addition of a "little" blue might make the key a tad more "neutral"?
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#6 David Mullen ASC

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Posted 19 December 2010 - 05:28 PM

Is it possible that the key light is more like 2700k and perhaps the addition of a "little" blue might make the key a tad more "neutral"?


Sure, I'm assuming that his tungsten key is actually 3200K, but obviously it could be a bit below that. On the other hand, a minor drop could easily be fixed in timing.
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#7 Ari Schaeffer

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Posted 20 December 2010 - 11:02 AM

I find that people always forget that you lose more light with CTB then CTO. It's fine if you have the intensity to play with, but if I need every bit of light I'd rather balance 5600 to 3200 then vice versa. It should be noted there are trade offs in doing this. Tungsten units are typically less expensive by far when compared to a 5600k unit like an HMI...but they are less efficient and run hotter usually.

If anything it really makes you appreciate the human eye and it's ability to maintain color consistency on the fly. Here's an interesting blog post I found the other day on a photographer that has a shift of color temp between his left and right eye. http://www.pixiq.com...ce-of-your-eyes Something I hadn't considered people deal with, pretty interesting.
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#8 Tim Tyler

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Posted 20 December 2010 - 03:00 PM

Lowel Lighting has a nice color temp guide on their site now.

Color Temperature & Color Rendering Index DeMystified
http://www.lowel.com...emystified.html
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