I am wondering if Rodenstock rear lens elements are usually marked somehow with a serial number or something. I have a 150mm APO-Sironar-N, marked 72 degrees 1990s serial number, that I am 90% sure has the wrong rear element. It's rear element is something like 31mm wide and doesn't "flare" out at all- it's just a straight barrel. It also has no markings whatsoever that I can find. Is there any definitive way of telling what the rear element actually goes to?
I've left my 150mm Sironar back in the UK but I'm fairly sure there's no markings on the rear element's barrel,and it does flare out. Here's Rodenstock's data-sheet.
I think the OD of the rear elements should be 42mm
Sounds like you have 150mm f5.6 Xenar rear elements they are 31mm OD.
Ian
No, there is nothing on the back group. I just checked a new 210mm N that we have in stock. Sorry I couldn't check a 150N but it is no longer available.
Put the lens together. Open the press focus, open the aperture to 5.6. Turn out all the lights, point the lens out the window and hold a white card behind the lens. Move the lens away or towards the card until you see a sharp image on the card. What is the diameter of that circle and how far away is the card from the lens?
The diameter of the rear group on a 150N is 42mm. The diameter of the rear group of the 100N was 31.5mm.
Are you measuring the actual rear element diameter or the diameter of the rear mount diameter? The push-on rear cap will be stamped 42mm inside the cap for the 150N.
The length of a 150N from the edge of the front rim to the edge of the back rim was 51mm. How long is yours?
Those measurements will tell you if the lens is properly put together.
Check the rear elements to see if they are Multi-coated as well. Xenar cells aren't.
Could also be 150mm f9 G Claron rear cells, their OD is 32mm, and they aren't MC either.
Ian
Ok I aimed the lens out the window and it focused at about 90mm from the rear element- I probably should have measured from the aperture which would have made it 100mm or so. The rear Rodenstock cap is marked 31.5mm and the rear element is multicoated. So all signs point to a 100N rear element?
Incidentally I did try it on an actual camera and the lens at least illuminated 4x5 with some room for front rise and fall. It also appear sharp on the ground glass but I think I detected some strange aberations in spots.
Where did you get the lens? Was it new when you got it? When did you get it?
Schneider sold a Triple convertible Symmar for a very short spell.
The newer Sironar's like yours are near Symmetrical like the Symmar's but the earliest ones weren't.
In theory any Symmar/Sironar cells can be combined to provide a variety of focal lengths. That's how all Triple Convertibles work and the most famous is the Cooke XVa.
However you've ended up with a dud lens.
Ian
I bought the "lens" mainly for the shutter and I paid far less than the going rate of a modern Copal #0 on E-Bay. The last owner was aware that the lens elements weren't right somehow. I have no idea where he got it. He was told by someone who does Polaroid->4x5 conversions that "the lens doesn't cover 4x5" (which it actually seems to).
I guess more testing is in order to see if this lens could produce a decent image. I took a few test shots on 4x5 that came out pretty good. But it was focused at about 10 feet instead of at infinity so maybe not a good test.
OK, so makes sense now
Test it, it may be far better than we think, that's a we the readers
Try f22 . . . . . . . .
Ian
Here is a shot with the mismatched elements lens. I believe this one was at f/22. I did drop the front standard a fair amount in this shot and there is some vignetting at the bottom probably because of this. The image is fairly sharp though, not bad at all really. I have taken shots with no vignetting so I think it does cover 4x5 if your careful.
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