210mm Sinaron S ?

[M. Johnson]

Why does a 210mm f/5.6 Sinar Sinaron S have a 310mm image circle and a 210mm f/5.6 Rodenstock Sironar N have a 301mm image circle? They are supposed to be the same lens but the specs don't match up. I own the Sinar and it does cover 8x10....just. Any ideas?

[Michael S. Briggs]

Probably someone transposed the digits when typing. The specs that used to on Sinar's website listed the correct 72 degrees for the angular coverage. If you want more confusion, 210 mm focal length and 72 degrees angular coverage gives a third diameter to wonder about: 305 mm. Probably the exact end of the coverage can't be defined this precisely, anyway.

[GPS]

The 72° is a rounded number.