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  1. #1

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    Anyone know something about this lens???

    I just "inherited" a brass barrel lens. I have no idea of the focal length or of it's coverage. It has very few markings apart for the aperture scale. There is a VIII engraved on the barel. There are 2 elements (maybe groups?, I can't tell if there is more than one piece glass glued together). Any info would be appreciated.
    Attached Thumbnails Attached Thumbnails lens1.jpg   lens2.jpg   lens3.jpg  

  2. #2

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    hi pasto

    it might be a rapid rectalinear lens
    http://en.wikipedia.org/wiki/Rapid_Rectilinear

    you could google a variety of different lens types
    to see what they are

    this is a tessar
    http://en.wikipedia.org/wiki/Tessar

    this is a petzval
    http://en.wikipedia.org/wiki/Petzval_lens


    this book has a lot of them
    http://books.google.com/books?id=OJr...20lens&f=false

    good luck !
    john

  3. #3

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    Thanks John. I'll mount it on a lens board and see what it gives me

  4. #4
    Ian Grant's Avatar
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    In the first two phototos the sets of cells are mounted at the wrong end of the barrel, the wider set has a slight lens hood built in and should be at the front leaving the smaller diameter set at the threaded end.

    There were an awful lot of unmarked R-R lenses made in the late 1900's, some by larger companies others unknown. Finding the approx Focal lenght is easy just focus a tree or something distant onto a piece of paper and measure the distance of the aperture ring to the paper.

    Often these R-R lenses had relatively long FL's so the one on my half plate camera is marked Wray 8"x5" (coverage) with a S.No. there's no FL marked but it's actually a 300mm/12" f8. Aside from the aperture scale there's no other markings on my 6" lens on my quarter plate camera.

    Thesew lenses are ideal for using with a Thornton Pickard shutter, they came in two types one for front mounting the other between lens board and lens.

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    Ian

  5. #5

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    Thank you Ian. I had not noticed but of course you're right that one end has a small shade that even has what seem like filter threats on the inside. This end surely belongs on the front of the barel. This has obviously been played with before getting to me. I also note that the rear element is placed convex facing away from the diaphram while the front element is facing convex in. The diagrams I've seen showing the elements in a rapid rectalinear lens always show the convex side of the element facing out. Any ideas?

    Also, how does a Thornton Pickard shutter attach to the lens? How can I tell if it's the fron or the rear mounting type? There are a few on sale now...
    Last edited by Pasto; 01-25-2012 at 12:59 PM. Click to view previous post history.

  6. #6
    Ian Grant's Avatar
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    Luigi, the TP shutters that fit the front of a lens have a rubber ring that fit's the hood part, there's a small screw that tightens to hold it in place. They used to sell different thicknesses of these rubber adaptors. The ones that fit behind the lens usually have an interchangeable front plate to allow different lenses to be used with the same shutter, there will be a brass lens flange or at least the holes where one has been fitted.

    Ideally you're better off with a T and Instananeous (not a Snapshot) these allow speeds between 1/15 and a 1/90 as well as T, some have speed indicator dial. Unless in mint condition don't pay too much for one.

    Ian

  7. #7
    ath
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    When you shine a (weak) red laserpointer though the lens you can see if it is one piece of glass or two glued together. The laser is intense enough to make the transition visible.
    Regards,
    Andreas

  8. #8

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    OK, I'll start my research on TP shutters. I just shined my laser pointer into the lens. Can't tell about the number of elements as I'm not quite sure what to look for.

    Any ideas about the correct orientation of the elements (convex out or in)?

  9. #9
    Mustafa Umut Sarac's Avatar
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    Pasto ,

    Let me try to add Andreas post. When you point the laser in to front elements group , you must see the boundries between first , second or more elements together. Dont shine green laser in to your eye if you have. Use red one and conduct a slow research. For each element , there must be a different glass and there must be a old adhesive between elements. Try to illuminate them with diffracting the laser beam on them and try to see what is there for front and back.

    If it is an expensive lens and if you want to see what is the lens design , a museum or repair person could have an answer if you want to spend least some postage money.

    But there is an other option , use your lens with your photographs and if it have a significant bokeh , aberrations , it might reveal the design.

    By the way , there can be a air gap between lens elements and may be you couldnt be sure.

    Dont forget to post your pictures. It really helps you.

    Umut

  10. #10

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    I finaly mounted the lens on a board and tried it on my 4x5. The lens projects a very bright image. I measured the focal length at about 210mm. This is consistent with the focal length as calculated by the diameter of the diaphram at a given f-stop. It also projects a very large image circle. With maximum shifts and rise/fall I could not reach the end of the image circle at f/8. Saw the edge with front swings and tilts of course. I estimate the coverage that I could verify at about 8 x 8 inches. I want to use it on my Century Universal (once I finish rebuilding it), and I'm hoping it will cover the whole 8x10 negative stopped down to f/32-64. My fingers are crossed

    Thanks to all for the input. I'll post some images once I get some....
    Last edited by Pasto; 01-28-2012 at 03:22 PM. Click to view previous post history.

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