Trying to find details - Bausch and Lomb 18 inch EF?

[hoffy]

Hi Folks,

I have just come across a lens and am wondering if anyone would know anything about it.

According to the stamping on the housing its a Bausch & Lomb. Stamped on the front element holder it is stamped 18 In EF. With my rudimentary knowledge of lenses, I am assuming that it is a Petzval, as there are simply one element at the front and another element at the rear.

Can anyone tell me anything about this lens? Can anyone tell me what kind of coverage I would expect? I am hoping to get at least full plate coverage.

Also, how do I calculate the aperture and check the focal length of this lens?

Cheers

PS - sorry about the name in the title. I know its supposed to be Bausch!

[hoffy]

Just to add some details. The barrel is around 3 1/2 inches long. The front glass is around 1 1/12 inches in diameter. The barrel appears to be Nickel as opposed to brass. The lens seems a bit small and I'm afraid the aperture will be quite small for what is stamped on it.

[goamules]

It's a projector lens. They made dozens of types and lengths and speeds. Half are triplets, half Petzvals. Usually if there is a black fitting that holds one group screwed into the rear, it's a Petzval. Both have a black fitting in the front, usually engraved with focal length. If one black fitting is just in the front, and the nickle goes all the way to the other end, it's a triplet. But you have the lens, you can unscrew it and tell US what it is. A Petzval needs two elements in the rear, so yours is either missing that, or was a triplet and is missing the inner one. It probably won't properly cover anything if it's missing an element.

Determining coverage, focal length, and speed, are all explained in this forum over and over if you do a search. Also, the lens says it's an 18 inch Equivalent Focal length.

[hoffy]

By black band, do you mean on the lens retaining ring (for use of a better term). If that is what you mean, then yes, the front and the rear are both black and not nickle like the barrel.

[goamules]

This one is likely a Petzval, note the black group at the rear of the barrel. Triplets screw into the front only, and the rear is nickle with no black fitting. If yours looks like this, it should be a petzval. But if one of the rear elements is missing, it's not complete.

https://s-media-cache-ak0.pinimg.com/736x/96/8e/de/968ede8593ac6064da7d72bb9edf22f6.jpg

And this 17" i just sold, was a Triplet:

https://c2.staticflickr.com/2/1575/26148906004_53a5774e46_b.jpg

[hoffy]

Thanks Garrett.

It looks a bit like both! The front ring looks like the front ring on the triplet, but the back ring can most certainly be removed.

Based on the info I gathered, though, the lens is going to be painfully slow. If it is an 18 inch (which it appears that it probably is - I still haven't checked it myself though.), I rate it as around an F12. Would that be correct?

The good thing is that I was given the lens, to return if it doesn't meet my needs. I was hoping that the lens was a bit shorter and a bit faster as I want to use it for portraits.

Cheers again.