What's the difference between Schneider center filter III and IIIa?

[Aaron Rocky]

I couldn't find any info of IIIa at schneider website. Can it be used on SA 75/5.6?

[Walter Glover]

Aaron,

Both have a 67x0.75 thread on the rear and an 86x1 thread at the front. The gradation differs however.

The IIIa is for the 90mm 1:8 Super-Angulon

The III is for either the 65mm or 75mm 1:5.6 Super Angulons.

Furthermore there is a IIIb for the 58mm XL and IIIc for the 47mm XL

[Tom Westbrook]

Here's the Schneider document about their current center filters if others can't find it: http://www.schneiderkreuznach.com/pdf/foto/CENTERFILTER.pdf

[Aaron Rocky]

There is no mention of IIIa in the link above. I found it in the achieve:
http://www.schneiderkreuznach.com/archiv/pdf/centerfilter.pdf