I am looking at purchasing the Calumet version of the Rodenstock N 150mm. I have noticed in an old Rodenstock flyer that has a description of the Sironar S and N lines the S series description refers to having ED glass. No such claim is made for the N series... Has this just been omitted from the description? What exactly is the difference in the two lines? The elements/group count is the same, and so is the diagram.

Other than a reference about the N series being for general photography and the S being for "professional" photography the only other difference I see is the image circle size.

Daniel

-- Daniel Sayre (arcadianet@firstinter.net), September 10, 2001

Answers

The N does not use ED glass is optimized to perform optimally from 1:10 to infinity and has to be stopped down further to reach optimal aperture.

the APO SIRONAR S is corrected from 1:5 to infinity, hits optimal aperture sooner, holds optimal erformance over more stops, has higher contrast and greater resolution and also covers a larger circle.

Many published articles also comment on the S having outstanding Bokah compared to many other lenses.

-- Bob Salomon (bob@hpmarketingcorp.com), September 10, 2001.

Bob, and Daniel -

I can tell you from my experience in owning and using both that the Apo-Sironar-S lenses have superb rear-bokeh (character of the out-of- focus parts of the image behind the plane of focus), but so do the Apo-Sironar-N lenses. It's probably extremely difficult at best to tell them apart with respect to that characteristic.

I'm a big fan of the Apo-Sironar-S lenses myself, but in situations and for users where size, weight or cost are overriding considerations, the Apo-Sironar-N types are also excellent, beautiful lenses for which no apologies need be made...

-- Oren Grad (orengrad@world.std.com), September 10, 2001.