Rodenstock Sironar 210 5.6 convertable

[d._kevin_gibson]

Does anyone know anything about these lenses? It looks like a

convertable focal length version. I only have Nikon and Fuji lenses.

 

 

What about the coverage/image circle for this?

[pete_andrews]

The Sironar is Rodenstock's version of the Symmar - a fairly standard 'plasmat' style lens. The 'converted' image quality is very poor, but if you just use it as a straight 210mm, it's a fine lens.<p>I've never looked up or measured the coverage of mine. All I know is that it's more than enough for all the movement I'm ever likely to need on 5x4.<br>I can't find any data for the Sironar on the web, but it's so similar in design to Schneider's Symmar, that the data for the Symmar will probably be very close. (If it hasn't got "apo" or "digital" in the name, then Rodenstock don't seem interested in supporting it!)<p>Anyway, the Schneider Symmar has a 70 degree image cone @f/16, which is about a 297mm image circle @ infinity.

[michael_briggs2]

An old Rodenstock brochure gives the coverage diameter for "exacting demands" as 266 mm at f11 and 286 mm at f22.

 

For use as a convertible, it is suggested to remove the rear component and use only the front component, which will approximately triple the focal length. (This is opposite to the approach that was suggested by Schneider for the Symmar, i.e., Schneider suggests removing the front component.) The quality after moderate stopping down is described as "satisfactory", compared to the "maximum sharpness" of the full lens. You will have to experiment to see if you find the quality of the converted lens satisfactory.

[bob_salomon]

use only the front component, which will approximately triple the focal length.

(This is opposite to the approach that was suggested by Schneider for the

Symmar, i.e., Schneider suggests removing the front component.) The quality

after moderate stopping down is described as "satisfactory", compared to the

"maximum sharpness" of the full lens. You will have to experiment to see if

you find the quality of the converted lens satisfactory.

 

 

Both techniques were commonly recommended by both companies.

 

By removing the rear element you add protection for the outer shutter blades

and get longer shutter life.

 

By removing the front cell you expose the shutter blades and will probably

shorten their live from exposure to dust, handling, etc.

The effect on film will be identical.

[pete_andrews]

My convertible 210mm Sironar is marked with a secondary focal length and aperture scale. The focal length is certainly not tripled by converting the lens, in fact it's not even doubled. The secondary FL is marked as 400mm f/12, from memory.<br>I don't have the lens in front of me to check, and I would never use it converted in any case, but I do know for sure that the focal length isn't tripled.<p>I tried the convertible feature out when I first got the lens, and discovered that only the front assembly gave the marked converted focal length.<p>Using the rear assembly alone gave me a shorter FL of something like 350mm, and it seemed to me that the geometrical distortion was worse when using the rear group.