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purple flares on florescent lights?


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#1 Bryan Harvey

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Posted 24 January 2008 - 09:21 PM

Hi,
I've noticed that I sometimes get purplish flares intruding into my shot when a florescent light is just outside the frame, just grazing the edge of it. (VARICAM + Canon HJ11x4.7 lens) I'm shooting a doc series in prisons, mostly handheld verite - so no control of lighting. I don't experience the flares if the entire florescent light is in the shot, only when it is grazing the edge.

Any tips on how to deal with that?

thanks!

Bryan Harvey
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#2 Chris Keth

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Posted 24 January 2008 - 09:28 PM

It's only with fluorescent fixtures? I was under the impression that the color of flares was mostly dependent on the coating of the various elements in the lens.
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#3 Michael Nash

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Posted 25 January 2008 - 04:00 AM

It sounds like it's just the way that that lens flares -- purple is not uncommon in video lenses. The best way to avoid it is to flag the lens or frame it out. Unfortunately, hand-held with a wide lens usually doesn't allow for enough coverage by a mattebox or lens hood, and colored flares are hard to see in a B&W viewfinder. I've gotten used to looking for foggy or "veiled"-looking areas in the viewfinder to spot flares when operating (in conjunction with knowing when the lens is prone to be flared).
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#4 Jonathan Bowerbank

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Posted 25 January 2008 - 06:19 AM

You gotta stop trying to use purple gels as flags ;)

Really though, it's just the spectrum of the Kinoflo's light being broken up and altered in the lens coating and various elements. Sometimes I get flares from tungsten sources that appear blue, it happens.
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#5 Jonathan Bowerbank

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Posted 25 January 2008 - 06:20 AM

This is an edited double post that happened, somehow

Edited by Jonathan Bowerbank, 25 January 2008 - 06:20 AM.

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#6 John Sprung

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Posted 25 January 2008 - 02:08 PM

It's only with fluorescent fixtures? I was under the impression that the color of flares was mostly dependent on the coating of the various elements in the lens.

I'd guess that coatings probably trump everything else in this case.

Purple is the mixture of red and blue, the far ends of the spectrum. Therefore, we can rule out refraction and diffraction. Flourescents have the infamous green spike, so if anything they'd be deficient in red and blue. That pretty much leaves coatings as the probable cause.

Try testing it with an incandescent source, and let us know what you get.




-- J.S.
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