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Thread: Lens Knife?

  1. #1

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    Lens Knife?

    Hi,
    I'm brand new to large format photography and am looking at camera options. In the description of a Chinese rangefinder camera vendor, there is mention of a "Lens Knife." Googling the term doesn't lead to results. I gather it's a metal piece that matches the focus and/or field of view of the rangefinder camera to the lens as the bellows is adjusted. Since there is nothing on Google I'm guessing that "lens knife" is possibly not the correct term. Does above description sound familiar to anyone? Is there a different name? Is this something one has to make or have made for each focal lenght lens?
    Thank you for any feedback!

  2. #2
    8x10, 5x7, 4x5, et al Leigh's Avatar
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    Re: Lens Knife?

    Hi Joerg, and Welcome Aboard.

    I've never heard the term "lens knife", nor anything that might resemble that in translation.

    Some rangefinders do rely on cams to control the movement of one of the mirrors.

    - Leigh
    If you believe you can, or you believe you can't... you're right.

  3. #3
    Tracy Storer's Avatar
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    Re: Lens Knife?

    Very probably a rangefinder cam specific to each lens focal length.
    Tracy Storer
    Mammoth Camera Company tm
    www.mammothcamera.com

  4. #4

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    Re: Lens Knife?

    If Linhof rangefinder cams were actually knifes they would probably be illegal in some states. And forget getting on an airplane with it!

  5. #5
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    Re: Lens Knife?

    Quote Originally Posted by Leigh View Post
    Some rangefinders do rely on cams to control the movement of one of the mirrors.
    Quote Originally Posted by Tracy Storer View Post
    Very probably a rangefinder cam specific to each lens focal length.
    What Leigh and Tracy said - it's almost certainly referring to rangefinder cams. If you use plenty of imagination, the shape of the cams for the Linhof Technika rangefinder could arguably be described as resembling a knife.

  6. #6

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    Re: Lens Knife?

    I was able to find a picture (see link below). Apparently, this brass part is made specifically to a focal length. The person who posted this picture called it a "focusing blade". The google result for "focusing blade" is the same as it is for "lens knife". I understand what this thing does (kinda), but I am trying to figure out how hard (if not impossible) it is to get something like this for a different focal length. It may be unique to just one camera though I'm thinking there are probably more out there using something like this.

    http://photobucket.com/gallery/user/...anAuanBn/?ref=
    Any thoughts?

  7. #7
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    Re: Lens Knife?

    There are repair technicians who are willing and able to carve cams for custom focal lengths. This is easiest to do if you want a cam for an existing system like Linhof or Horseman where cams in a wide range of focal lengths have been provided by the manufacturer, and matching a new focal length requires only modest adjustment to an existing blank or finished cam. If you have to start from scratch to come up with a cam for a very different focal length in a camera that is not based on an existing cam system, it will likely be more difficult, time consuming and expensive.

  8. #8

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    Re: Lens Knife?

    Quote Originally Posted by Oren Grad View Post
    What Leigh and Tracy said - it's almost certainly referring to rangefinder cams. If you use plenty of imagination, the shape of the cams for the Linhof Technika rangefinder could arguably be described as resembling a knife.
    Actually doesn't take too much imagination to think of it as a knife...
    Click image for larger version. 

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  9. #9

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    Re: Lens Knife?

    ...now how about that lens sharpener?

  10. #10

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    Re: Lens Knife?

    Lens sharpener??? Isn't that what digicams do???

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