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Tri-X Confusion


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#1 Alessandro Machi

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Posted 23 April 2007 - 02:20 PM

That explains your problem right there. Even I have trouble exposing Tri-X correctly!


I have pilfered this quote from another topic on another cinematography.com forum because I recently got to shoot six different super-8 stocks and the one that I had the most difficulty with was Tri-X. Does the filter lower the ASA rating by 2/3 of a stop, or not?
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#2 Mark Dunn

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Posted 23 April 2007 - 03:26 PM

The 85A preferentially absorbs blue so it's going to have a tonal effect similar to that of a red filter. But Tri-X is panchromatic, so apart from darkening the blues I'd say yes, you could go with 2/3.
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#3 Mike Crane

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Posted 23 April 2007 - 07:49 PM

The 85 filter is removed via a switch in the film compartment when a roll of B/W film in inserted into the camera. This is the purpose of the 85 filter notch. So, the answer is no, the in camera 85 filter does not affect your exposure settings.
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#4 Rick Palidwor

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Posted 23 April 2007 - 09:12 PM

The 85 filter is removed via a switch in the film compartment when a roll of B/W film in inserted into the camera. This is the purpose of the 85 filter notch. So, the answer is no, the in camera 85 filter does not affect your exposure settings.


Mike is right. When you insert a b&w cartridge it disables the built-in filter, so if you want to experiment with an 85 filter on b&w you need an external one but I think you'll do better with traditional b&w filters, like green, red and yellow. The 85 won't be that noticeable.

Alex, try over-exposing the tri-x by at least a stop. The white's get really nice and the blacks hold.

Rick

Edited by Rick Palidwor, 23 April 2007 - 09:12 PM.

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#5 Alessandro Machi

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Posted 23 April 2007 - 10:16 PM

You mean the camera is overriding my choice to use the 85 filter. :angry:

I thought at one point I moved the filter switch while in the automatic expoosure mode and I thought the exposure shifted 2/3's of a stop. Well, it should be easy enough to test that option tomorrow.
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#6 Rick Palidwor

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Posted 23 April 2007 - 10:23 PM

You mean the camera is overriding my choice to use the 85 filter. :angry:

I thought at one point I moved the filter switch while in the automatic expoosure mode and I thought the exposure shifted 2/3's of a stop. Well, it should be easy enough to test that option tomorrow.


I don't have a b&w cart here to check, but what could be happening, if you see an aperture change, is that you are "telling" the camera you are shooting under daylight or tungsten, since b&w film has slightly different ISO ratings based on the type of light. With colour film the different ratings for tungsten or daylight are including the filter factor (the film only has one rating) but b&w has two ratings and I sometimes wonder how the camera knows what you are shooting with. The difference is so sight that I have never worried about it, but I am curious what you learn.

And try over-exposing the tri-X. It's counter intuitive to overexpose reversal film, but try it, you might like it.
Rick

Edited by Rick Palidwor, 23 April 2007 - 10:23 PM.

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