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Colour filter opposites


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#1 G McMahon

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Posted 06 July 2006 - 10:36 AM

In the past I have white balanced through an opposite colour gel to give a colour bias I want, or shot a macbeth with a colour opposite to what I require to get the colour I require corrected in post. This saves on gels and stops taken from lights.
My question is, If I like the look of colour gel, example, lee filter colour lilac tint 169, how can I find the exact opposite colour gel on the colour wheel to shoot a macbeth or white balance through to correct to get my lilac tint 169?
Please enquire if I haven't worded this question well.
Thanks all,
Graeme
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#2 Ram Shani

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Posted 06 July 2006 - 11:40 AM

i think you have to hold a color wheel and loot for the same tint as the pink filter and then look for the opposite color on the wheel and that should be your filter
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#3 G McMahon

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Posted 06 July 2006 - 12:05 PM

Thank you, but that can be subjective. I should have been more specific, can I read the spectural chart to find the exact oposite.
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#4 John Pytlak RIP

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Posted 06 July 2006 - 12:14 PM

If you know the spectral transmittance of the filter you want to emulate, the complement will be a filter that has density in the parts of the spectrum where the other filter has tranmittance.

A practical way to find a filter's complement is to find a filter that when combined with the filter you are working with produces a NEUTRAL gray for the light source you are dealing with. For example, if you combine a pale magenta filter (e.g., a Wratten CC20M) with a pale green filter (e.g., a Wratten CC20G), the combination will be nearly gray -- the two filters are complements of each other.
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#5 Michael Nash

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Posted 07 July 2006 - 03:01 PM

Usually you end up using a combination of gels to get just the right color when white balancing, for example a combination of plusgreen and cto to get purple. It's usually trail and error.

One thing to be aware of though is that video cameras don't give perfect color reproduction throughout the spectrum. So even if you did find a gel that's the perfect theoretical complement ("opposite"), there's no guarantee white balancing through it would give you the color you want. And especially with purple -- that's one of the colors that video has a hard time reproducing accurately. The camera essentially has to borrow extra information from the blue channel to keep the luminance up, and the color comes out "blue."

And to make matters worse :( , such subtle color balance often gets thrown out of whack with post production and display systems that may be out of your control. It's frustrating sometimes, because even something as simple as a warming filter can make the image come out excessively red or saturated when you see it on air. NTSC = Never Twice the Same Color.

I prefer to adjust the RGB levels and gamma in camera whenever possible, to more accurately "paint" a white balance. Not all cameras let you do that, though.
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#6 David Mullen ASC

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Posted 07 July 2006 - 05:06 PM

Spectral response in film is also uneven by design, usually to get accurate fleshtones.

I think there are limits to how much you can find the opposite color gel to some oddly mixed-dye color like lavender, white balance to that oppposite color, and end up with exactly the same shade of lavender. You'll just need to test or carry lots of subtle swatches of color to get the correct effect through white balancing (i.e. you try an color combination, white balance through it, and then add some pale gel to adjust.)

But you may find that some colors don't even look the same on different types of monitors either once you start working in very off-shades. And exposure affects how the color appears in terms of intensity.
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#7 John Pytlak RIP

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Posted 07 July 2006 - 06:42 PM

Of course you could always white balance without the filter, then shoot through the filter that has the color you want.
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#8 Chris Cooke

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Posted 08 July 2006 - 07:32 PM

Of course you could always white balance without the filter, then shoot through the filter that has the color you want.


True, but Graeme was refering to 169 Lilac Tint which is a lighting filter, not a camera filter. And I know you understand this John but others may not: Lighting filters (gels) are not optically pure so you will get unwanted aberations and vignetting in your image especially at a deep stop and/or close focus such as macro.
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#9 Chris Keth

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Posted 09 July 2006 - 03:44 AM

True, but Graeme was refering to 169 Lilac Tint which is a lighting filter, not a camera filter. And I know you understand this John but others may not: Lighting filters (gels) are not optically pure so you will get unwanted aberations and vignetting in your image especially at a deep stop and/or close focus such as macro.




I would just get a swatchbook and see what filter adds to that one to make neutral grey. Hopefully it's one that is also available, or has a similar counterpart that is available, in gelatin or glass camera filters. Other than that, it's ballparking it, probably.
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#10 John Pytlak RIP

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Posted 09 July 2006 - 12:11 PM

True, but Graeme was refering to 169 Lilac Tint which is a lighting filter, not a camera filter. And I know you understand this John but others may not: Lighting filters (gels) are not optically pure so you will get unwanted aberations and vignetting in your image especially at a deep stop and/or close focus such as macro.


Yes, any filter used in front of the lens should not have optical imperfections that would degrade the image.
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