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Thread: Building a AV-Xenotar 150mm 2.8 lens for 4x5

  1. #1

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    Building a AV-Xenotar 150mm 2.8 lens for 4x5

    This is a new project I'm working on, got the lens for a good (still not cheap) price.
    It is a AV-Xenotar. And it looks fantastic. Nice and black. I don'nt know how the final quality will be.

    I have taken the lens apart already but I can't find what type of lens it is.

    For the shutter I will be using a Copal 3S. Still waiting on some parts before I get going.
    Coverage will be probably around 90 to 110% of 4x5 at infinity.

    The scheme on the first photo is a more correct schetch. The second photo is more to give an idea of the thickness and curve of the glass.
    I think it is closer to a Sonar type lens than a Plannar (Xenotar) type lens.

    Click image for larger version. 

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    Click image for larger version. 

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    Here is a website with some lens designs
    I think its closest to the Zeiss Sonnar 50mm 1.5 1932.

    What do you think?

  2. #2

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    Re: Building a AV-Xenotar 150mm 2.8 lens for 4x5

    It is a slide projector lens, not a taking lens.

  3. #3

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    Re: Building a AV-Xenotar 150mm 2.8 lens for 4x5

    A projection lens has a particular optimization in the design.

    Ideally, a projector illumination has a condenser, this means that ideally only a particular ray goes from an spot on the slide to the projected spot (say subject), so in theory optimization is made for that ray to provide image quality. Instead a taking lens has many different rays going from a particular spot in the subject to the film, so the lens needs an optimization that's valid for all those rays.


    This means that, optically speaking, the projection lens may not be a top performer option for image taking, still the projection lens may deliver many creative effects that can be very nice, but IMO it is not to perform like a Xenotar made for cameras.

  4. #4

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    Re: Building a AV-Xenotar 150mm 2.8 lens for 4x5

    Thanks for the info.
    I know it's a slide projector lens. And I know it's not a xenotar, that is a planar type scheme.
    My question as to what type of lens it is, is for the location of where I wil place the shutter and aperture. I'm looking to put it as close to the 4th lens as possible to keep closed down aperture vignetting to a minimum.

  5. #5

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    Re: Building a AV-Xenotar 150mm 2.8 lens for 4x5

    Quote Originally Posted by Xifoideus View Post
    is for the location of where I wil place the shutter and aperture.

    First, locate your Rear Nodal point. Hold the lens to project on a wall, say you are in a room and you project on the wall sharp (say 15m or more) distant buildings that are seen from a window of the room. Your Rear Nodal point will be 150mm far from the wall you are projecting on, inside the lens suposedly.


    You may try to place your iris there, or a bit farther from the wall, if you have no interference with glass.


    You may place shutter where you want, still you should need an smaller shutter if located in a nodal point.


    This is my understanding, perhaps an optician may add more or correct that.

  6. #6

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    Re: Building a AV-Xenotar 150mm 2.8 lens for 4x5

    I have made a cardboard aperture around f22 ish. I have tried that in various locations. By complairing the preview on the ground glass I was able to see the best location. Just behind the 4th lens is the optimal spot to place it. Now I know where I have to cut the lens.

  7. #7

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    Re: Building a AV-Xenotar 150mm 2.8 lens for 4x5

    Quote Originally Posted by Xifoideus View Post
    I have made a cardboard aperture around f22 ish. I have tried that in various locations. By complairing the preview on the ground glass I was able to see the best location. Just behind the 4th lens is the optimal spot to place it. Now I know where I have to cut the lens.
    Rollei sold that lens for their 6x6 slide projectors. One version offered a built-in diaphragm which allowed improved quality projection with non glass mounted slides.
    Why donít you try to find a picture of that version. That would show you where you should place your diaphragm.

  8. #8

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    Re: Building a AV-Xenotar 150mm 2.8 lens for 4x5

    There's at least 2 types of AV-xenotar 150/2.8s, one that covers medium format, and one that will cover 4x5. It looks like you have the latter type hopefully. Indeed it is a bit like a sonnar design. I've seen good results with folks using these as taking lenses.

  9. #9

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    Re: Building a AV-Xenotar 150mm 2.8 lens for 4x5

    Quote Originally Posted by Pere Casals View Post
    A projection lens has a particular optimization in the design.

    Ideally, a projector illumination has a condenser, this means that ideally only a particular ray goes from an spot on the slide to the projected spot (say subject), so in theory optimization is made for that ray to provide image quality. Instead a taking lens has many different rays going from a particular spot in the subject to the film, so the lens needs an optimization that's valid for all those rays.


    This means that, optically speaking, the projection lens may not be a top performer option for image taking, still the projection lens may deliver many creative effects that can be very nice, but IMO it is not to perform like a Xenotar made for cameras.
    that's not at all how a condenser works, or how light works, and projector lenses are not optimized in any such way.

  10. #10

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    Re: Building a AV-Xenotar 150mm 2.8 lens for 4x5

    Quote Originally Posted by EdSawyer View Post
    There's at least 2 types of AV-xenotar 150/2.8s, one that covers medium format, and one that will cover 4x5. It looks like you have the latter type hopefully. Indeed it is a bit like a sonnar design. I've seen good results with folks using these as taking lenses.
    The one he has has HFT coating. That was Rolleiís propriety multicoating and this lens was from a 6x6cm Rollex slide projectors. Probably one from the AF projectors as the ones from the P11 did not have HFT coating.

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