What is this brass lens?

Discussion in 'Large Format Cameras and Accessories' started by Fotoguy20d, Oct 11, 2009.

  1. Fotoguy20d

    Fotoguy20d Subscriber

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    Anyone have any thoughts as to what this lens might have been for originally? Any thoughts if it'll be fun on 4x5? It measures around 3 1/4" long and 1 1/2" outside diameter (those are for the barrel, not the glass). There's no thread on the outside for mounting so where would it have gone? Perhaps premature to ask since I don't have it in hand yet.

    Thank,
    Dan
     

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  2. bdial

    bdial Subscriber

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    It's probably some sort of projection lens. Maybe a Petzval design. The lenses for lantern slide projectors and similar were often just fitted into a tube that allowed the lens part you have to slide in and out for focusing.

    If you focus an image onto a light surface through a window or similar setup, you can estimate how much it might cover, what sort of image it might produce, and it's focal length. There is a good video on the mechanics of this at Jason Brunner's site; http://www.jasonbrunner.com/videos.html

    For mounting it on a camera, you can make up a lensboard, and bore a hole just big enough for the lens, fit the lens into the hole, then finish it off with some gaffer's tape or black electrical tape. The result won't be pretty, but it will work.

    For picture taking, you'll need to calculate the f number, which is covered in Jason's video. Finally, you'll either need slow film or a camera with a built-in shutter, such as a Speed Graphic.
     
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  3. Barry S

    Barry S Member

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    From the design, size, and focal length it looks like an early movie projection lens. Almost certainly a Petzval--it should be perfect for using on a 4x5. You may see some vignetting in the corners at infinity, but it should have a good amount of swirl. Looks to be about f/4.
     
  4. Dan Dozer

    Dan Dozer Subscriber

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    Looks definitely like a projection lens that may or may not be adaptable to a lens board - you can always try this. Unscrew either the back or front lens element and try using just that portion of the lens. I tried it with a projection lens similar to yours and got a beautiful very soft focus look that get's fuzzy towards the outsides - great for head and shoulders portraits. To calculate the F-stop -focus the lens at infinity and measure the distance from the lens to the film plane. Divide into that the diameter of the glass and that's your F-stop. Example: lens focuses at 6 inches at infinity and lens is 1 1/2" in diameter - F-stop is 6/1.5 or F4.
     
  5. Fotoguy20d

    Fotoguy20d Subscriber

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    As follow-up, I got the lens yesterday. It's a petzval, it vignettes 4x5 as predicted, but I haven't had a chance to try it out in a swirl inducing environment (and probably won't for a few days). For mounting, I used a pacemaker lens board with flange for a #3 acme, wrapped a piece of paper towel (folded over several times) around the barrel and threaded it in. Not a super tight fit but good enough that the lens wasn't slipping. A little black tape to seal it up and I can shoot with it.

    Dan