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Thread: How to use a triple convertible lens.

  1. #1

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    How to use a triple convertible lens.

    I've acquired a mint Ansco 8x10 camera with six new Lisco holders. The camera includes a Protar VII Triple convertible lens. I've never shot with anything but current Schneiders etc.

    The front element is a 23 1/4" and the rear is a 18 7/8".

    The faceplate on the No.5 Universal Shutter shows the f/stop scales for the 23, 18 and the combined (I assume) focal length of 12"

    Question is, if I only use one element such as the 18 7/8", do you always put it on the front of the lens so the shutter isn't exposed to the air or do either always go on the rear?

    Secondly, if I do use them both as a 12" lens, does the higher element always go in front or does it matter?

    Also, the highest speed is 1/50 sec and my shutter checker says it is slow at 1/25 sec. Does anyone have a favorite shutter repairman they would suggest?

    Just got the box of film and heading to the coast this weekend.

    Thanks for the help.

  2. #2

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    Re: How to use a triple convertible lens.

    With the Protar VIIs, the single element always goes on the rear - the position of the aperture helps with correcting some of the aberrations that are there with the single cell (that get corrected by the symmetry when both are used. When using both cells, the longer focal length goes in front. When using single cells,, be prepared for the bellows focal length to be greater than the focal length because the nodal point lies outside the glass.

    I'm guessing that you have a fairly large shutter (Betax # 4 or 5 or similar). You might have to resign yourself to a top speed of 1/25 or thereabouts. Just too large for the springs to drive the mass of moving parts any faster. I have two Betax #5 and 1 Ilex # 5 and they all reach top speeds of only around 1/20th or so.

    Enjoy the lens - it makes surprisingly good images (even when converted, especially with B&W).

    Cheers, DJ

  3. #3

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    Re: How to use a triple convertible lens.

    Ron Wisner said in testing some of his protars performed better with the shorter cell in front, so you might want to try it both ways. The advice above is generally considered the way it is supposed to be done, however.

    For shutter repair Carole at Flutot's is well thought of, but getting that lens faster than 1/25th may be trouble no matter what.

    More than a few people say single cell protars aren't much good. I suspect this is largely due to a failure to account for focus shift. If focused wide open, single cells will be a bit out of focus stopped down to f:32, which is minimum I'd suggest if you are expecting reasonably sharp edges. Recheck your focus with a good loupe after stopping down and adjust focus so that the lens is in the middle of the focusing distance that seems sharp on the ground glass. Or, to put it another way, stopped down that far there will be a zone as you rack the lens in and out where the loupe shows the image sharp in the middle. Set your focus in the middle of that zone. The results will be much better.

    For the single cells, you can easily make a scale of what would be appropriate f stops converted to your single marked apertures. Or you can write them in since that big shutter has so much handscape on the front for making notes. (I've done the math for this and carry it in a notebook, I can send you the apertures for the single cells in mm if you send me a p.m.)

    I think you'll find that combined you have an outstanding lens there, and that the single cells can save the day when you need a longer lens and they're all you've brought. The single cell performance even when stopped down to f:32 or f:45 may not be terribly sharp at the edges (depends on format, of course) but in a contact print you'll not see the fall off and with modest enlargements to 2x or 3x the negative will be quite acceptable to you. With single cells and an adjustment for focus shift the center sharpness is remarkably good.

  4. #4
    loujon
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    Re: How to use a triple convertible lens.

    Quote Originally Posted by Kevin Crisp View Post
    For the single cells, you can easily make a scale of what would be appropriate f stops converted to your single marked apertures. Or you can write them in since that big shutter has so much handscape on the front for making notes. (I've done the math for this and carry it in a notebook, I can send you the apertures for the single cells in mm if you send me a p.m.)
    Quote Originally Posted by Dave Henry View Post
    The faceplate on the No.5 Universal Shutter shows the f/stop scales for the 23, 18 and the combined (I assume) focal length of 12"
    Hey Kevin

    It seems Dave's shutter has the appropriate scales for both the combination FL as well as both single cells. So he seems to be set as far as that goes .

    I will second all the information provided by both DJ & Kevin. Very sound and useful information from both men indeed.

  5. #5
    Unwitting Thread Killer Ari's Avatar
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    Re: How to use a triple convertible lens.

    Jumping in here with a question regarding the Turner-Reich convertibles.

    I have a 12-21-28 and I'd like to know if anyone has a link for using it in its multifarious configurations (couldn't find a definitive link).

    Thanks

  6. #6
    Big Negs Rock!
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    Re: How to use a triple convertible lens.

    Ari, if it's a TR lens, it is the same lens I have. Edward Weston shot with it and is rumored not to like the 21" configuration. I don't like it either, but the 12" & 28" are fine. I shoot with the 12" all the time.
    Mark Woods

    Large Format B&W
    Cinematography Mentor at the American Film Institute
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    www.markwoods.com

  7. #7
    Unwitting Thread Killer Ari's Avatar
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    Re: How to use a triple convertible lens.

    Mark, thanks; I usually use the 12" as well.

    I can only reach 25" on my 8x10 bellows, so the 28" is out of my scope for the moment.

  8. #8

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    Re: How to use a triple convertible lens.

    back to the OP, Carol Miller (Flutots) fixed my last Ilex 5 but the 1/50 is still not 1/50. Be happy if it's consistent and you know what it is.

  9. #9
    multi format
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    Re: How to use a triple convertible lens.

    Quote Originally Posted by Ari View Post
    Jumping in here with a question regarding the Turner-Reich convertibles.

    I have a 12-21-28 and I'd like to know if anyone has a link for using it in its multifarious configurations (couldn't find a definitive link).

    Thanks
    hi ari

    i am not able to find a definitive link either
    although there is this one on apug, and it also
    references the new cooke triple from a few years ago
    http://www.apug.org/forums/forum187/...x14-12x20.html

    typically the way a triple convertible works
    is both elements together are the smallest focal length ( in your case 12" )
    the front element removed is the mid-focal length ( in your case 21 " )
    and the rear element removed, and the front placed behind the shutter is the longest focal length (28 " )

    have fun !
    john

  10. #10
    Unwitting Thread Killer Ari's Avatar
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    Re: How to use a triple convertible lens.

    Thank you, John, exactly what I needed to know.
    I'll have a look at the APUG link as well.

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