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Thread: Experience with "Convertible" lenses?

  1. #1

    Experience with "Convertible" lenses?

    Hi, I was hoping some of you out there may be able to help me, I am potentially looking at buying a convertible lens, am looking at either the Schneider Symmar 300mm - 500mm or the Symmar 360mm - 620mm. Was just wondering if anyone had any examples to possibly show (both on the long and short ends) and any suggestions overall really.. Also, any idea on what price I might be looking at for these two options?

    ok, thanks a lot. Any suggestions or advice would be greatly appreciated!

    Cheers

  2. #2

    Join Date
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    Re: Experience with "Convertible" lenses?

    Actually, some of them work really well, but the best way to use them is usually to remove the front element so you better have a LOT of bellows draw available. I mean a LOT!
    Wilhelm (Sarasota)

  3. #3

    Re: Experience with "Convertible" lenses?

    Oh dear... Had completely forgotten about that one, has been a while since i have used large format gear! I have a Chamonix 45N-1, it says it has a maximum bellows draw of 395mm, any lens suggestions (that don't weigh a ton) that would make use of this maximum bellows? Any telephotos that would enable this longer bellows draw? Or would I be better off with the "360mm f10 Fujinon A"?

    Ok, thanks again, much appreciated!

  4. #4

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    Re: Experience with "Convertible" lenses?

    My experiences with Schneider convertible Symmar lenses is this. The lens works well with both elements, but is significantly softer converted. This you can ameliorate with aperture and by using a strong filter (orange, red, etc.) to eliminate part of the spectrum and thereby eliminate the effect of the inevitable chromatic aberration.

    My Schneider convertibles were single-coated and prone to flare. I got rid of them for that reason.

    BTW, I have 240mm and 180mm Fuji A lenses and a love them. The 360mm f/10 should be great for your camera as long as you don't need to focus too close. I have a Nikkor M 450mm that is my longest lens. That needs 20+ inches of bellows draw to use effectively and makes for a pretty big package in use. I can't imagine using a 600mm lens on a 4x5... I can always crop.

    Best,

    Doremus

  5. #5

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    Re: Experience with "Convertible" lenses?

    Quote Originally Posted by mandonbossi View Post
    I have a Chamonix 45N-1, it says it has a maximum bellows draw of 395mm, any lens suggestions (that don't weigh a ton) that would make use of this maximum bellows? Any telephotos that would enable this longer bellows draw? Or would I be better off with the "360mm f10 Fujinon A"?
    If you need a maximum reach with limited bellows draw - but want to focus closer then infinity- then a tele is the way to go. A 400mm Fujinon T will work nicely, as will the 360mm Nikkor T-ED, 360mm or 500mm Schneider Tele Xenar lenses.

    Given a non-tele 360mm lens and 395mm of bellows draw, how close can we get ?

    1/F = 1/D + 1/E where F = focal length, D = distance, B = Bellows Draw

    F = 360mm, B = 395mm

    1/360 = 1/D + 1/315
    1/D = 1/360 - 1/395
    1/D = 0.0027 - 0.0025
    1/D = 0.0002
    d = 5000 mm
    Distance = 5 meters or 16.4 feet, and that's pulling the bellows as far as it will go.

    It may be easier to find one of those tele lenses than a 360mm Fujinon A - and less money for that matter. The Fujinon A will cost more than your camera, which begs the question of whether the cart is leading the donkey, or vice versa

  6. #6
    kevingm
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    Re: Experience with "Convertible" lenses?

    My 4x5 has a maximum bellows draw of 365mm, and the Schneider 400 telephoto works very well on it. It requires only 285mm to focus at infinity, so 395mm gives you a reasonable amount of room to focus closer than that.

  7. #7

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    Re: Experience with "Convertible" lenses?

    Quote Originally Posted by Bill_1856 View Post
    Actually, some of them work really well, but the best way to use them is usually to remove the front element so you better have a LOT of bellows draw available. I mean a LOT!
    But the Rodenstock Sironar specifically stated that you remove the rear group. This also protects those delicate aperture and shutter blades not to mention makes it less likely that things get into the shutter itself when the rear group is removed.

    And they only start to get sharp, regardless of brand, at very small apertures when converted.

  8. #8

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    Re: Experience with "Convertible" lenses?

    Quote Originally Posted by Bob Salomon - HP Marketing View Post
    But the Rodenstock Sironar specifically stated that you remove the rear group.
    My Schnieder Symmar has the converted f-stop and focal length stamped on the rear element, so I've always thought that meant to remove the front element. Ive never used it for that, so I can't say how well it works

    Click image for larger version. 

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  9. #9

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    Re: Experience with "Convertible" lenses?

    Schneider seemed to recommed removing the front group. Rodenstock the rear group.

  10. #10

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    Re: Experience with "Convertible" lenses?

    I have a 240/420 Symmar. It cast a nice image on the ground glass but I don't think I've ever actually used it. At some point I realized it was basically the same as my 9 1/2" Dagor -stopped down, I'm very happy with it converted on my 8x10

    Dan

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