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white balancing thorugh minus green?


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#1 Jim Feldspar

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Posted 26 October 2006 - 07:32 AM

I heard that there are new specially warming white balance cards out and then some special purpose
ones such one designed for use under flourescent lights that is supposed to give much superior flesh
tones than using a regular white card because this new card incorporates some kind of minus green
in itself somehow. Sounds great and I'd like to buy the kit but I don't have the money right now.

If I'm in a situation with some( less than modern) greenish flourescents that I can't change out or gel;
would holding a sheet of minus green tightly to the lens hood -flat like a filter - and white balancing
through that do the trick?

To whomever invented the minus green card, sorry dude. When I can afford it, I'll buy your kit.
Good luck!
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#2 Bob Hayes

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Posted 26 October 2006 - 08:44 AM

You have the right idea. But you want to add + green to your card or filter. This forces the camera to over correct and add more magenta. I find the regular white balance under fluorescent light doesn?t get enough of the green out. I will sometimes white balance through a light + green gel in front of the lens to correct this out.
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#3 Jim Feldspar

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Posted 26 October 2006 - 11:30 AM

You have the right idea. But you want to add + green to your card or filter. This forces the camera to over correct and add more magenta. I find the regular white balance under fluorescent light doesn?t get enough of the green out. I will sometimes white balance through a light + green gel in front of the lens to correct this out.


Thanks, but I'm not sure that I understand exactly.

" But you want to add + green to your card or filter." Are you saying to use plus green,
NOT minus green and furthermore to place it not in front of the lens but on top of the white card?


"I will sometimes white balance through a light + green gel in front of the lens to correct this
out." Are you saying that you'll gel just one of the floursecents and put the white card under
that or would you even light up the white card with a tungsten light going through a plus green
gel? If you could clarify I would greatly appreciate it. Thank you.
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#4 Michael Collier

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Posted 26 October 2006 - 04:25 PM

Yes, plus green is correct. White ballance is an inverse thing. To get a warm image, you ballance off a blue surface. If you use neg-green (magenta) you will actually induce more green, since the camera adds green to try and make the image white. Place plus-green in front and you get more magenta, to balance out the greenspike. you can use a filter, but what I did was scan the neg green, print it out and use that as your white card. I have 3 warm cards based on 1/4 CTB, 1/2 CTB, 1 CTB, and the plus green.

I find the regular white balance under fluorescent light doesn?t get enough of the green out. I will sometimes white balance through a light + green gel in front of the lens to correct this out.


I find the same thing. I have always wondered why cameras cannot register green as well, since there are far more green pixels in a bayer CCD, and in a pixel shift block, its the only one not shifted. Seems to me like there would be more resolution in the green to time it out. Maybe manufacterers weight the whiteballance to largely ignore.
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#5 Jim Feldspar

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Posted 26 October 2006 - 04:53 PM

Yes, plus green is correct. White ballance is an inverse thing. To get a warm image, you ballance off a blue surface. If you use neg-green (magenta) you will actually induce more green, since the camera adds green to try and make the image white. Place plus-green in front and you get more magenta, to balance out the greenspike. you can use a filter, but what I did was scan the neg green, print it out and use that as your white card. I have 3 warm cards based on 1/4 CTB, 1/2 CTB, 1 CTB, and the plus green.
I find the same thing. I have always wondered why cameras cannot register green as well, since there are far more green pixels in a bayer CCD, and in a pixel shift block, its the only one not shifted. Seems to me like there would be more resolution in the green to time it out. Maybe manufacterers weight the whiteballance to largely ignore.


Thanks for clarifying, Michael.

"what I did was scan the neg green, print it out and use that" ---So, put a minus green gel
in a scannner and print on white paper, right? Would a white balance card from scanned
full CTB give you a sunset look, then?

(If I had a scanner I'd just go do it and see but I can take some gels to someplace that
has one - just want to make sure.)
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#6 Michael Collier

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Posted 26 October 2006 - 05:34 PM

Yes, CTB makes for a very warm look. I used a scanner set up for scanning negs. The light has to come from behind the filter, not in front. I suppose you could use a regular scanner, just back the filter up with something white. I will see if I can find the color swatches and email them to you so you can print them out. It takes a little trial and error to find exactly what your looking for, since every printer is a little bit different. I went through a few printings before I found colors that looked good to me with the printers I was using.


***EDIT I wanted to clarify I scanned the plus green, not the neg green

Edited by Michael Collier, 26 October 2006 - 05:35 PM.

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#7 Jim Feldspar

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Posted 26 October 2006 - 09:46 PM

Yes, CTB makes for a very warm look. I used a scanner set up for scanning negs. The light has to come from behind the filter, not in front. I suppose you could use a regular scanner, just back the filter up with something white. I will see if I can find the color swatches and email them to you so you can print them out. It takes a little trial and error to find exactly what your looking for, since every printer is a little bit different. I went through a few printings before I found colors that looked good to me with the printers I was using.
***EDIT I wanted to clarify I scanned the plus green, not the neg green



Wow, that would be awesome - thanks!
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#8 Dino Giammattei

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Posted 30 October 2006 - 09:15 AM

I have found that for my purposes, even the factory ½ warm card is like whacking the picture with a hammer. I scanned and PS'd several versions of the ½ and cut the chroma. I now use those more than the factory cards.
If they made a quarter, eighth, and even sixteenth, I would buy them in a minute. The finish on the real cards is almost indestructable. Really a great product, just needs a few more options.

Tired Old Dino
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#9 Joseph Carney

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Posted 31 October 2006 - 12:57 PM

Some excellent info here. I have related questions..
If the Flos have a color temp of 3200K and a CRI of 90, is the green issue reduced.
Same question for flos with 5400K and 6400K and CRI of 90 or better.

btw, I'm using high frequency electronic ballasts at 60khz.

Edited by Joe Carney Sr, 31 October 2006 - 12:57 PM.

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