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#1 Scott Bryant

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Posted 23 May 2007 - 05:49 PM

When you are shooting 200 ASA Tungsten balanced film outdoors and you use an 85B filter this effectively changes your ASA to 125. When I meter this scene, should i meter at 125 ASA with the filter in front of the white dome? or should I meter at 125 w/out the filter? Or are either of those correct? I know this is very basic but i can't seem to think about it the right way.
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#2 David Sweetman

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Posted 23 May 2007 - 06:05 PM

When you are shooting 200 ASA Tungsten balanced film outdoors and you use an 85B filter this effectively changes your ASA to 125. When I meter this scene, should i meter at 125 ASA with the filter in front of the white dome? or should I meter at 125 w/out the filter? Or are either of those correct? I know this is very basic but i can't seem to think about it the right way.

Metering at 125 ASA already compensates for the light loss, which is apparently 3/4 of a stop. So metering through the filter would double this, giving you a 1 1/2 stop loss, causing you to underexpose by 3/4 of a stop.

But in any case, you wouldn't meter through the filter, you would figure out what amount of light is lost through the filter and adjust your ASA accordingly. Remember every time the ASA doubles, it's twice as sensitive, or one stop faster.
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#3 David Sweetman

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Posted 23 May 2007 - 06:15 PM

- also, it would already be acounted for in the 125asa figure, but unfiltered, wouldn't the stock be effectively faster in daylight as opposed to tungsten? If so, what should it be rated, unfiltered?
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#4 Chris Keth

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Posted 23 May 2007 - 06:23 PM

- also, it would already be acounted for in the 125asa figure, but unfiltered, wouldn't the stock be effectively faster in daylight as opposed to tungsten? If so, what should it be rated, unfiltered?


Unfiltered, you would rate it as normal, but it would turn out very blue. Only B&W films have different speeds for different lighting spectra, because they are slightly more sensitive to blue light then they are red.
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#5 Sam Wells

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Posted 23 May 2007 - 06:25 PM

David - in the interest of accuracy it's 2/3 of a stop - think thirds, ..... 200, 160, 125 ......

-Sam
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#6 Scott Bryant

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Posted 23 May 2007 - 06:26 PM

Thanks guys I appreciate it.
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#7 David Sweetman

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Posted 23 May 2007 - 06:44 PM

David - in the interest of accuracy it's 2/3 of a stop - think thirds, ..... 200, 160, 125 ......

-Sam

gotchya...125 seemed to fall on a fourth-mark on the one-stop difference between 100 and 200, sorry for the misinformation
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#8 mageshkumar

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Posted 24 May 2007 - 06:54 AM

When you are shooting 200 ASA Tungsten balanced film outdoors and you use an 85B filter this effectively changes your ASA to 125. When I meter this scene, should i meter at 125 ASA with the filter in front of the white dome? or should I meter at 125 w/out the filter? Or are either of those correct? I know this is very basic but i can't seem to think about it the right way.



Just turn your meter to 125ASA and take the reading. Its enough. The filter factor u can compensate in the meter itself. what ever the filter u may use, calculate and change the ASA in the meter and take the exposure reading.
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#9 David Mullen ASC

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Posted 24 May 2007 - 09:51 AM

"mageshkumar", if your real name is Magesh Kumar, please go to My Controls and edit your Display Name to reflect this -- your Display Name has to be a first and last name, as per the forum rules, and it's unclear right now. Thanks.
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