Rodenstock Sironar 150/450?

[Mark Volle]

I have purchased a Rodenstock Sironar 150mm. There are NO additional letters and the lens is labeled 1:5.6 but the scale on the shutter also lists 450mm and f 16-64. I am guessing that this is for use with only the rear element.

Is this type of lens corrected enough with just the rear element that I can expect crisp color images or only B&W with a narrow band filter?

I bought it for use as a 150mm so the 450mm would only be a bonus.

Thanks

[Ernest Purdum]

I think it is unlikely that taking the front cell off a 150mm lens would result in the rear cell working at 450mm. Convertibles are more apt to have a ratio of single cell to combination of under 2:1 than 3:1.

I would guess that a previous owner used the shutter with another lens or that the shutter was a replacement on the Sironar and had earlier been used on a longer lens.

Using the rear cell of the Sironar by itself would probably have some results usually considered unsatisfactory (distortion, poor definition, etc.) but if your curious, give it a try. You might find the results interesting.

[Frank Petronio]

Dagor had an auction last week for another Rodenstock Sironar that was set up as a convertible with an extreme range - I forget exactly but I think it was something like a 180/720 pairing or 4x range. All the Schneider Symmar convertibles I've seen have been in the 2X range.

I have never heard of this type of convertible lens before but now your post makes me suspect there is more to the sotry and maybe it is really true. Or Dagor is pulling an elaborate hoax on us? ;-)

[Steve H]

I haven't seen anything like this either. It sounds like someone remounted the lens in a shutter that was once used for a 450mm lens.

[Steve Hamley]

Folks,

http://www.photo.net/bboard/q-and-a-fetch-msg?msg_id=00FUWl&tag=

Steve

[Arne Croell]

The old Sironars (1st generation) were convertible. I'
ve handled a 210mm a while ago and from what I remember, the focal lengths (and sizes) of the front and back group where quite different, so this is probably right. These Sironars are not very common, so many people have never seen them. They are easily recognized by the large difference of the front and back diameters, the front lens is much bigger than the back.

[Michael S. Briggs]

In http://www.photo.net/bboard/q-and-a-fetch-msg?msg_id=00FL9i I relate some information from an original Rodenstock brochure on the Sironars. Some Sironars were marketed as convertibles, converting to about three times their focal length, so this is likely the original lens and shutter.

[j.e.simmons]

I have a 210mm plain Sironar from 1972 mounted in a #1 Copal that's marked for two focal lengths. I think the longer length is about 500mm, but I don't have it in front of me to check. I have used the rear element alone only a couple of times, and only with B&W - so my recommendation is try your lens with color and see how well it does.

juan

[Arne Croell]

Note that in the link provided by Michael Briggs it is stated that ones uses the FRONT group with the Sironar for the longer focal length, which is contrary to common knowledge as well as the practice with all or most other convertible lenses.

[Ernest Purdum]

It hadn't occurred to me that the lens would have differing cells front and rear. I associate configurations like that with "triple" convertibles having three aperture scales. Since apparently Rodenstock didn't want the rear cell used by itself, maybe there were corrections in the front cell lacking in the rear.

Arne Croell. A front mounted single cell may have pincushion instead of the barrel distortion typical of rear mounted cells. Which is better? I'd just as soon have neither one.

[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!!!!