B&L Cinephor petzval - aperture?

[f/stopblues]

Forgive a LF newbie, but I have this Bausch and Lomb Cinephor projection lens and I realized I don't have a basic piece of exposure info.. the aperture. Hopefully you all can help, or point me in the right direction at least.

Here's the info I have:

B&L Cinephor Series I
Marked 4.50 (I assume that's 4.5 inches)
"In E.F." (what does that mean?)

If we don't know the exact aperture for this particular lens, is there a good starting point to run some bracketing tests from? I've had the lens for quite a while but just picked up a 4x5 press camera so I can finally play! I've shot 4x5 monorail before, but this older stuff is a new adventure.

Thanks for your help!
Chris

[jcoldslabs]

Chris,

For a ballpark f/stop for your Cinephor divide the diameter of the front glass element into the focal length, which in your case is 4.5". If the front diameter is around one inch or so this would give you an effective wide open shooting aperture of f/4.5.

This works with just about any lens, and although it is not the most exact method it will work just fine. I have a handful of Cinephors and I have determined all of their shooting apertures this way. Enjoy the lens; they are fun to shoot with.

I believe "E.F." stands for "equivalent focus" which is the focal length of the lens, as opposed to "B.F." or "back focus" which would measure the distance from the rear element to the film plane when focused at infinity.

Jonathan

[Fotoguy20d]

EF is effective focus.

It's probably around an f2-2.5 lens from the cinephors I've seen. Yours might be a petzval, but it also will probably be challenged at covering 4x5 (the 5-5.5s I have darken corners slightly).

Dan

[f/stopblues]

Thanks for the info. That helps a lot! We'll see what happens when I take it for a spin on Friday.

[Dan Dozer]

Something to consider trying - I have an Ilex Projection Petzval lens that has a focal length of only about 4" with both elements and the image circle size is much too small for the 8 x 10. However, if I use only the front or back elements, it's focal lengths are at about 7" and 12" depending on which element I use and both will cover 8 x 10. You won't get a sharp focus lens doing it this way, but the soft focus effects are really unique and I work with it all the time with portrait work.

[Richard Rankin]

Actually, a lot of the Cinephors have a 'reducing' ring inside the barrel. If you have one, you need to use the inside diameter of THAT for your calculation, not the glass. If you can get it out, your lens will be faster, but most I've seen are difficult to remove.