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Plus-X Tungsten vs. Daylight


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#1 Will Montgomery

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Posted 24 October 2005 - 09:02 PM

I have some 7231 Plus-X Negative stock ready to shoot, and I noticed something that is confusing me.

The 3200k Tungsten rating is 64, while the daylight rating is 80. Why would the Tungsten/Daylight issue come up on a B&W stock? What type of filter would be used inside on B&W that would reduce the sensitivity?

While the light temperature is different, I thought light was light to meter and the reason stocks are rated differently is because you must use filters to correct for color issues.

I am sure I'm missing something very basic, so please be patient with me.
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#2 David Mullen ASC

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Posted 25 October 2005 - 12:17 AM

The different ratings don't mean that you need to use filters. B&W film is less sensitive in the red end of the spectrum, so you need to rate it slightly slower in tungsten lighting, that's all. Or to put it another way, the film is more sensitive to the blue end of the spectrum. Tungsten has more red; daylight has more blue.

I usually use the tungsten rating when shooting outdoors through red or orange filters (plus compensate for the filter factor of course). It's only 1/3 of a stop different from the daylight rating anyway.
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#3 Alain LeTourneau

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Posted 25 October 2005 - 11:25 AM

The different ratings don't mean that you need to use filters. B&W film is less sensitive in the red end of the spectrum, so you need to rate it slightly slower in tungsten lighting, that's all. Or to put it another way, the film is more sensitive to the blue end of the spectrum. Tungsten has more red; daylight has more blue.

I usually use the tungsten rating when shooting outdoors through red or orange filters (plus compensate for the filter factor of course). It's only 1/3 of a stop different from the daylight rating anyway.




David,

What about when shooting through deep yellow...#12, #15?


Alain LeTourneau
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#4 Dickson Sorensen

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Posted 25 October 2005 - 12:12 PM

David,

What about when shooting through deep yellow...#12, #15?
Alain LeTourneau


To know the exact compensation for a particular filter you should consult the manufacture of that filter. That's not always practical so what I have always done is to read with my spot meter through the filter onto a gray card with and without and make a note how much light this filter absorbes. Or you can use your incedent meter with the flat cell and take a comparison that way. Do this in the light you are shooting in, ie sunlight or interior tungsten. I also use this method for determining how much to compensate for black stockings on the lens. Polarizes come in many different densities so I always check them this way also.
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