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  1. #1

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    Protar VII mismatched cells

    I have shutter that has a Protar VII 14 inch front element and a Protar VII 9 inch rear element.

    Is that correct? I thought the front and rear elements have to match.
    "There are two ways to avoid most trouble in life: live below your means... and within your seams."

  2. #2

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    Quote Originally Posted by Frank R View Post
    I have shutter that has a Protar VII 14 inch front element and a Protar VII 9 inch rear element.

    Is that correct? I thought the front and rear elements have to match.
    Thee front and rear elements of Protar VII convertibles have different focal lengths. This gives three possible focal lengths, of each of the cells when used by itself, and combined.

    Sandy King

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    I don't know that lens as well as I wish I did, but isn't it a convertable... in which case the front and rear cell are expected to be different. What does the aperture scale look like -- one set of numbers or three sets?

  4. #4

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    Both Bausch & Lomb and Zeiss made Protars could be bought with the front and back cells the same focal length or with the two cells of two different focal lengths. On the Zeiss made Protars I've seen with the front and back cells the same focal length, the cells had consecutive serial numbers. Based on some information on Zeiss made Protars I have, the equivalent two focal lengths of the two cells you have (22 and 35 cm) combined give a focal length of 15.5 cm.
    David

  5. #5
    colrehogan's Avatar
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    I have seen threads like this on the LF forum. I have a CZJ Protar VII in which both elements are 69 cm. However, the serial numbers on each element are different (but sequential- I think).
    Diane

    Halak 41

  6. #6

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    Quote Originally Posted by BrianShaw View Post
    I don't know that lens as well as I wish I did, but isn't it a convertable... in which case the front and rear cell are expected to be different. What does the aperture scale look like -- one set of numbers or three sets?

    I expected it to be a convertible but it has only one aperture scale on it.
    "There are two ways to avoid most trouble in life: live below your means... and within your seams."

  7. #7

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    Quote Originally Posted by David Lindquist View Post
    Both Bausch & Lomb and Zeiss made Protars could be bought with the front and back cells the same focal length or with the two cells of two different focal lengths. On the Zeiss made Protars I've seen with the front and back cells the same focal length, the cells had consecutive serial numbers.
    This is a B&L lens with a Century (CCC) shutter.

    The front number is 78342

    The front number is 81381


    Quote Originally Posted by David Lindquist View Post
    Based on some information on Zeiss made Protars I have, the equivalent two focal lengths of the two cells you have (22 and 35 cm) combined give a focal length of 15.5 cm.
    David

    Thanks, I was going to ask that question next.


    Now, if my shutter has one aperture scale, how do I use these lenses?
    "There are two ways to avoid most trouble in life: live below your means... and within your seams."

  8. #8

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    Quote Originally Posted by David Lindquist View Post
    Based on some information on Zeiss made Protars I have, the equivalent two focal lengths of the two cells you have (22 and 35 cm) combined give a focal length of 15.5 cm.
    David
    This leads me to wonder about the coverage. I thought this would cover 8x10, maybe even 11x14 but that 22 cm and 15.5 cm have me thinking it won't cover with those elements.
    "There are two ways to avoid most trouble in life: live below your means... and within your seams."

  9. #9

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    Thanks for the feedback. Any answers to the follow-up questions?
    "There are two ways to avoid most trouble in life: live below your means... and within your seams."

  10. #10

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    Quote Originally Posted by Frank R View Post

    Now, if my shutter has one aperture scale, how do I use these lenses?
    Frank,

    Does your aperture scale show fstops? If so, the widest aperture for the combined set would be 7.7. It would be 12.5 for a single element.

    For protar lenses, the manufacturers occasionally also supplied a single scale that gives the diameter of the iris opening. They did this because you can easily calculate the needed iris opening for a given fstop for any combination of these lenses. To do so, you focus the camera, then measure the distance from the center of the lens (iris location with both elements) to the inside face of the ground glass (film plane). Divide this measurement by the desired fstop and you will have the size of the iris opening needed for that fstop. Bellows factor correction is automatic with this method.

    I have attached a file that shows the various iris openings for desired fstops for the zeiss protar VII's. The iris opening shown corresponds to infinity focus.

    To use the single elements, just place them in back of the shutter/iris.

    Pete
    Attached Thumbnails Attached Thumbnails protarapertures.jpg  
    Last edited by roodpe; 10-07-2009 at 11:10 AM. Click to view previous post history.

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