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Doug Kerr
3-Jan-2007, 16:05
I recently acquired a nice Rodenstock Apo-Ronar 480 mm f/9 barrel lens.

The aperture ring is conventional, but it has a second scale, calibrated in mm, which seems to give the exit pupil diameter! (Perhaps useful with one form of the equation for depth of field!)

However, just in front of the aperture ring there is a curious lever, which moves through a slot, with a travel of almost exactly 90 degrees. It moves a ring inside the lens that doesn't seem to do anything.

Ny first thought was that it was a reminder of the aperture you planned to use, to facilitate resetting it after opening up fully to focus, but its travel doesn't seem to match that.

The ring inside has a somewhat curious exterior profile, but that might be the result of breakage. It is split at the point the little lever is attached by a screw. (As a result, when you pull the lever, it spreads the ring and prevents it from rotating). It looks as if it has a recess on its front side that could receive some circular plate.

It is almost as if this is intended to rotate an internal polarizer, although that seems far-fetched.

Does anyone know the purpose of this lever and ring?

Thanks.

Best regards,

Doug

GPS
3-Jan-2007, 16:09
Some of these process lens had a dial attached that calculated - well, something on some scale... ;-) Don't be afraid of it.

Bob Salomon
3-Jan-2007, 17:37
Do be afraid of it. Your lens has the slot for diskls used in the graphic arts process. That slot is where the disks went. Leave it open and light comes in. Tape it closed it has no purpose for photo applications.

Shen45
4-Jan-2007, 00:30
Excellent advice Bob :) You don't actually realise until you have processed the film and wonder why the image is not what it should be. I have a 360 Apo Ronar and use it as a barrel lens with a "sock shutter". The lens is heavy but really sharp.

Doug Kerr
4-Jan-2007, 11:26
Hi, Bob,


Do be afraid of it. Your lens has the slot for diskls used in the graphic arts process. That slot is where the disks went.

Aha! I see now how that would work. And the lever is just to close off the slot (which it does at one end of its travel) when no disk is in place.


Leave it open and light comes in. Tape it closed it has no purpose for photo applications.

Makes sense to me. No need for tape - because of the split in the ring where the lever is attached, the lever can't be used to rotate the ring!

Thanks for the insight.

Best regards,

Doug

C. D. Keth
4-Jan-2007, 22:00
It might be a good opportunity to formulate your own quick set of internal portrait filters to slip in. Things that are usually a pain in the ass to put on the lens could be quick and easy with that slot. For closeups in films, I have used saran wrap to very good effect, and womens' hose is a classic standby if you can find a brand you like that is thin enough. Also try a piece of glass with a thin spray of hairspray.