Rodenstock Sironar 150/450?

[Arne Croell]

Ernest, I agree, no distortion would be better. And the quality will be inferior to the combined lens. I made the remark because using the front group on its own is so unusual and everybody, me included, will normally tell people to put the single cell on the back for a convertible.

[Ernest Purdum]

Me, too.

[Mark Volle]

Lots of great information.

I would probably not have believed that the lens was actually convertable without the help. The rear element doesn't work and the front element is uselessly low contrast and soft at "wide open" (calling f16 open is a little stretch). Once you stop down to f22 the contrast instantly jumps back to an acceptable level.

Now I am anxious to go out and find a suitable test shot.

The front element is decidedly larger than the rear. It sounds like I do have what Arne and Michael have outlined.

I'll see what the distortion looks like.

Thanks

[Philippe Grunchec]

I have such a lens in front of me, with the double lettering. But if I remove the back cell, I get (wide open) a rather soft image... the length does not seem to be 450, may be 300 only! Help!!!!