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Exposure Adjustment For Filters


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#1 Ira Ratner

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Posted 10 November 2008 - 08:06 AM

I just ordered polarizing, red and yellow Cokin clone filters for b&w shooting. Since they're not Cokin brand, and I'm not metering through the lens, can I assume that my exposure compensations will be equal to the Cokins?

Yeah, I should have bought the Cokins, but there's no one on eBay selling them. And yeah again, I could ask the seller, but I'd rather ask for your input first.

Here's the red one:

http://cgi.ebay.com/...em=290018800609

And the Polarizer:

http://cgi.ebay.com/...em=290018800609
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#2 David Rakoczy

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Posted 10 November 2008 - 08:48 AM

The only way to tell (short of contacting the Manufacturer) is to Spot Meter thru the Filter and compare that to what you get Spot Metering the same object (e.g. Gray Card) without the Filter.

Edited by David Rakoczy, 10 November 2008 - 08:49 AM.

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#3 Ira Ratner

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Posted 10 November 2008 - 05:35 PM

The only way to tell (short of contacting the Manufacturer) is to Spot Meter thru the Filter and compare that to what you get Spot Metering the same object (e.g. Gray Card) without the Filter.


Uhhh...

Thanks for reminding me of what an idiot I am, Dave.

Am I THAT old that I couldn't figure that out for myself?

Yes.
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#4 Chris Keth

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Posted 10 November 2008 - 08:25 PM

Uhhh...

Thanks for reminding me of what an idiot I am, Dave.

Am I THAT old that I couldn't figure that out for myself?

Yes.


It was early in the morning. Anyway, make sure it is a neutral surface you spotmeter. Lightmeters don't generally have perfectly even spectral sensitivity. I don't know that it's enough variation to throw your exposure off enough to matter but I like to be thorough when I do that kind of thing.
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#5 Simon Wyss

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Posted 11 November 2008 - 05:09 AM

Since the test method for filter density is so simple you can readily rely on manufacturers' data unless they are false.
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Broadcast Solutions Inc