Bausch & Lomb 6 inch EF... f/1.4??

[Vascilli]

So I picked up a lens at auction today that was stuffed in a housing for a General Electric X-ray unit of some sort. Took it home and cracked it open and I can barely make out that it's a Bausch and Lomb 6 inch EF. Also references US patent 2,124,356, which is for a 100mm f/1.5 design. Oh yeah it has a red dot, too. (Or some sort of dot, all the text was red) Serial starts with CZ. With a tape measure I found the front element to be about 4.25" making it a 6" f/1.4? I put a 4x5 ground glass and it looked to roughly cover 4x5. (Probably a little less) The bulk of the body is still covered by a silver barrel that I can't for the life of me figure out how to get off. Hope it's not radioactive... What is this thing? Took a look at lens catalogs from the era and found nothing remotely similar. Hmmmm....

[Steven Tribe]

You will need to look through the Lens VM or medical catalogues.
Under B&L I found:

Photo-Fluorographic f1.5 150mm This was probably to record X-ray traces onto film using larger sizes
for better details than the very small 16mm films. This tended to be early postwar?

CZ could point to Carl Zeiss as the maker. There are many more candidates there around F1.5. Even an F0.8.

This is from the days of mass screening for TB.

[Vascilli]

Very interesting! If the serial is like other B&L products the C indicates it's a 1949 make. The Z would correspond to something else. (Medical products, perhaps?) Does B&L have a history of having Zeiss make their lenses? I'm not familiar with the Lens VM, can you provide a link or more info?

[Steven Tribe]

Lens Vademecum is available as a very reasonable download from CCHarrison.
www.antiquecameras.net will get you to his site. This is based on lenses which were available for examination in the UK and some other countries are not well covered - either qualitatively and quantitatively!

[NancyP]

This lens should not be radioactive. It may be from a fluoroscopy unit, essentially focusing the beam onto the phosphor-coated detection plate for real-time imaging. BTW, radioactive (thorium containing glass) lenses generally are slightly yellowish, unless treated with UV by a recent user. Oscilloscope lenses are even faster - f/0.9 or faster.

[Harold_4074]

The fluoroscopy guess is likely correct, but the lens would have focused the light from a phosphor panel onto film, not x-rays onto the phosphor plate. If we could focus x-rays using a glass lens, this would be a very different world and not necessarily for the better This was in the rather early days of image intensifiers, so a really fast lens would have been desirable--just like the fast Oscillo-Raptars for oscilloscope cameras, where things like flatness of field and resolution are traded off against recording speed.

I remember being "screened" for TB as a kid of about nine or so, which would have made it about 1958; I was mystified because there seemed to be no film involved, and I knew enough about x-rays and photography to wonder how it all worked. Adding to the confusion was what appeared to be a film camera that photographed each kid standing in front of the fluoroscope panel, probably for positive identification in case a TB case turned up (no fair sending in your healthy kid brother so that you don't get shipped off to a sanatorium...)

[Nathan Potter]

Yes Harold has it correctly. I would have guessed that the lens focal length would be fairly long and the wide aperture necessary for reasonable time of exposures. No doubt lens made by B&L. Certainly not used for focusing X-rays (1 to 10 angstrom units wavelength). I could use a lens that would do that, but the attenuation of X-rays in glass is quite high, probably 80 to 90% depending on the glass type and thickness.

It would be interesting to see how the lens performs. Let us know if you get a chance.

Nate Potter, Austin TX.

[NancyP]

My bad. I need to stir up my 40 year old Physics 101 memories.

[Vascilli]

I'll definitely try to rig something up to use it. It's incredibly heavy and really wide. If my Calumet C1 was in working condition I'd question whether even it could handle it.

[Vascilli]

So I made the worst lensboard ever out of cardboard from a box of tacos to block light and held the lens up by hand to my 8x10. Looks like at "portrait" distances (<10 feet) it may be able to cover 4x5. I'll have to try it out during daylight to see if it covers more. The question now is how to build a camera around this lens. Probably some sort of pipe... flange-back distance is so short bellows would be pointless.