Lens Identification - Guru Alert

[Steve Hamley]

Folks,

'm in a bit of a puzzle here trying to identify a lens. There are two jpegs attached of this unusual beast. It's a Bausch and Lomb f:4.5 Tessar marked "296.1mm E.F. Tessar f:4.5" with the usual Bausch and Lomb Rochester marking and a serial of 3233702. It is NOT marked Ic. It's in a large and heavy (really heavy) helical focusing mount, calibrated from 8 feet to infinity with distance markings at 8, 15, 25, 50, 100 and infinity. Unlike most Tessars, it stops down to f:45. The helical mount has about 49mm of extension.

I've plowed through the B&L literature on Seth Broder's site, and can't find anything listing such a precise focal length or the helical mount it is in. It seems obvious that it was attached to a fixed or non-focusing "something". If it's a projector lens, why the precise FL and the long distance scales? If it's an aerial lens, why the short distance scales?

Now why get so interested in an old uncoated Tessar? Well, other than curiosity, when compared to a 30cm f:4.5 coated Heliar, it has a far better transition to out-of-focus and shallower DOF than the Heliar, which would seem to violate the laws of optics given the difference in FL of 4mm or so. That would also possibly indicate the B&L was optimized for a different use than a standard view camera taking lens. It is quite sharp too, but just seems to have a smaller DOF which gives a nice 3D look.

So, any idea what this thing is?

Thanks,

Steve

[David A. Goldfarb]

The precise focal length is usually needed for a rangefinder or perhaps an autofocus enlarger. Kodak made some large autofocus enlargers, so it could be for one of those, but I'd have thought they would have Enlarging Ektar lenses. There were also two Veritos made for the Kodak autofocus enlargers (yes, a soft focus enlarging lens).

[Nick Zentena]

Process lenses are also marked to actual focal length but those tend to be slower.

Some sort of copy lens?

[Steve Hamley]

I'd thought about a copy lens and maybe that's what it is, given the f:45 aperture and precise focal length. I hadn't thought about an autofocus enlarger lens although I had thought maybe a manual one, but then why the helical mount? I don't think it's for an autofocus enlarger because the helical mount has a focus lock screw (the silver knob) and the lever it attaches to is clearly a finger pad and has the black enamel worn off the edge from operation which is visible in the first jpeg. A local commercial pro that's 85 years old and has seen flash powder in use says he's never seen anything quite like it, and he's been around repro cameras and the like.

Thanks for the comments,

Steve

[Ole]

I have several taking lenses, especially from Schneider and Zeiss, which are marked with actual focal length.

It might be a taking lens for a rigid (box) camera, in which case the exact focal length would be needed to mark the distance scale.

[John Kasaian]

It looks like some sort of aerial camera lens to me, though I'm not sure why a point of focus at 8' would be needed, unless the camera ship is a crop duster

[Dan Fromm]

John, aerial camera lenses are typically fixed focus, are collimated to the camera by screwing into/out of the cone or by changing the thickness of a shim between lens and body. I've dismantled both types, have never hit one with a focusing helical. At even odds, perhaps better, Ole has it right.

[John Kasaian]

Dan,
Peter Gowland did make an aerial camera with helical focusing---I'm not exactly sure why.

I have seen several aerial lenses with the precise focal length painted or otherwise marked on the barrel and tessars were quite popular for aerial work, and yet the
8' preset focus would indicate that it isn't off an aerial camera.
Perhaps it was used on a horizontal copy camera? But then 100' of track bed is a bit hard to for me to comprehend.

It is an interesting mystery!

[phfitz]

One more problem, I have 2 8x10 B&L tessar 1c lens, they are 1/2 that length. I don't think thats a 4.5 tessar.

[leicam5]

I have seen these kind of lenses on cinéma projectors, but the jpeg's are to small to be sure.

Philippe