Schneider center filter IIIa on SA 5.6/65 mm?

[Aender Brepsom]

Hello,

although it has been designed for use with the Super Angulon 8/90 mm, I was wondering if I could also use the Schneider center filter IIIa on the SA 5.6/65 mm which should in fact get the center filter III. The filter threads are identical, but maybe it is not as easy as it seems ...

Thank you for any information.

Cheers

[David A. Goldfarb]

I've compared these two filters (I own a III and a friend has a IIIa), and there is only about a quarter-stop difference between them in the center. If you already have the filter and the lenses, then run a test, and you'll see if it's adequate for your purposes. I use the III on the 90/8.0 S-A, so if you don't own either filter, I know that combination works fairly well. The III is also pretty good on the 75/4.5 Grandagon-N, even on 6x17cm.

[martin_4668]

the fall-off of different centerfilters are designed specifically for the lensdesign/focal lenght stated by the manufacturer. The fall off is not so much ine the lens design, but the distance from the center of the filmplane to the rearlens element vs. the distance from the corners of the filmplane. When using the Schneider 65 used on 4x5, the distance to the corners is about twice as to the center.....therrefore a centerfilter to even the loss of light....
Hope this wasnt to technical, english is not my primere language.

[Bob Salomon]

"the fall-off of different centerfilters are designed specifically for the lensdesign/focal lenght stated by the manufacturer."

Not necesarrily.

Rodenstock makes two 67mm center filters. One for the Grandagon-N lenses with 67mm filter thread (75mm 4.5 and 90mm 6.8) and the other for the 35 to 55mm Apo Grandagon lenses.

The two filters have different densities.