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Old 14th January 2009, 10:19 PM
lee l lee l is offline
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Quote:
Originally Posted by percepts View Post
Well I think the CYAN filters have a more closely matched curves to the 44A but if the film you are using doesn't have any sensitivity over 700nm then an 81 is pretty close.
Don't know what the sensitivity curves for orthochromatic films were but current ilford sheet film seems to have cutoff at around 550nm and kodak the same. So an 81 may work for you. And be a lot cheaper I expect. But it depends exactly what you are looking for. An 81 is a cooling filter for colour work which figures as it is a minus red filter.
Rob,

I believe you mistyped 550nm for what should be 650nm for the typical end of panchromatic B&W film sensitivity.

I think there's also a problem arising from the Wratten vs. B+W and other filter designations. The Wratten 81(A,B,C) series are mild warming filters, the 85 series are stronger warming filters, and the 80 series are cooling color balancing filters, often used for daylight film under tungsten lighting. The B+W designations for the Wratten 80 series equivalents are KB filters, which don't go to zero transmission in red and do increase in transmission in the deep red to IR spectrum. However the B+W 081 is a different filter, and passes 10% at 600nm and fully blocks at 650nm and longer wavelengths. It doesn't have a secondary passband in the deep red or IR according to the curve in my 1982 B+W handbook.

Well, I just went looking for B+W curves on the web since I have no good way of copying from my 1982 B+W handbook. Looks like the curve for the 081 has changed a bit, passing more red and IR, but still not rising in that region. In any case, the 081 is certainly a stronger cutoff than a CC40C cyan from B+W. Others make stronger CC filters.

B+W curves are here: http://www.schneideroptics.com/pdfs/...sionCurves.pdf

The full handbook is here: http://www.schneideroptics.com/info/...dbook_Full.pdf

The 470 is missing in the new literature, but you might find "new old stock" at some dealers. The 470 wasn't a huge seller.

Lee

Last edited by lee l; 14th January 2009 at 10:30 PM.
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