?? 125mm Fujinon-SW f/8 (ACTUAL Focal Length) ??

Discussion in 'Large Format Cameras and Accessories' started by Old-N-Feeble, Dec 22, 2017.

  1. Old-N-Feeble

    Old-N-Feeble Subscriber

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    RE 125mm Fujinon-SW f/8

    These have a slightly longer flange-to-film distance (infinity focus) than most lenses of the same 'advertised' focal length. I'm not an optics guy but it seems to me the 125mm Fujinon-SW f/8 is closer to 135mm focal length, hence the actual image size is closer to what a 135mm lens will render.

    Is this a valid supposition?

    ...
     
  2. dentkimterry

    dentkimterry Subscriber

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    According to Fuji that lenses flange focal length is 138.8mm. You sir are not crazy! You are correct!
    Terry
     
  3. OP
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    Old-N-Feeble

    Old-N-Feeble Subscriber

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    If that's true then my search for a 135mm lens with lots of coverage for 4x5, and 5x7 has ended. I have one of the older single-coated 135mm Fujinon-W lenses but it's a plasmat and hasn't the coverage of their 125mm SW lenses (Super Angulon design). The 135mm WF Ektars (double WA Gauss) have been selling for far more than I can afford to pay and they have the same coverage as the older Fuji-W. The 125mm Fuji-SW has nearly two more inches of coverage than either of the 135's mentioned.
     
  4. Craig

    Craig Subscriber

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    The SW series is a wide angle, is that what you are looking for? The 125mm SW has an image circle is 280mm @F22, so not quite 8x10.
    There is also the 125F5.6 W that has an image circle of 198mm @F22; and the CM-W series that has an image circle of 204mm.

    Flange distance is where the lens mounts on a board, not the focal length. As an example I have a 90mm mounted on my 8x10 to make panoramic photos. The Fuji has a longer flange focal distance than a Nikkor 90/8, so the Fuji sits a bit further forward on the board ( further from the film) than the Nikkor. Due to the thickness of my standards, I can infinity focus the Fuji 90/5.6 and I can't infinity focus the Nikkor. They are both 90mm lenses though.

    The 125mm SW is the longest of the wide angle lenses that Fuji makes, aside from a 300mm with a 720mm image circle!
     
    Last edited: Dec 22, 2017
  5. OP
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    Old-N-Feeble

    Old-N-Feeble Subscriber

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    I'm asking about the 125mm f/8 Fuji-SW with 280mm image circle at f/22.

    What I care about is the image size at the film. Given a flange focal distance of 139mm, will this lens provide similar image size on film as a typical 135mm lens (vs. typical 125mm lenses)? I'm an idiot regarding lens design but do realize the actual focal length varies depending on specific lens parameters.
     
  6. Craig

    Craig Subscriber

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    No, it will be smaller than a 135. Think of the flange distance as a mechanical thing for mounting the lens, rather than related to optical properties. Telephoto lenses have a flange distance that is much shorter than a non tele lens of the same focal length. For example a 300mm Tele with give the exact same magnification on the film as a 300mm non-tele, but the flange distance will be vastly different.

    Pick the focal length you want and basically ignore the flange distance.
     
  7. OP
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    Old-N-Feeble

    Old-N-Feeble Subscriber

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    Thanks, Craig. I was hoping for a different answer but I suspected this is the case.
     
  8. ic-racer

    ic-racer Member

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    I have that lens also and use it on 8x10; it does not even fit on my 4x5 camera. The focal length of the lens is listed as 125mm and the the flange focal length (Ff) is listed as 138.8mm. The Ff is an indicator of how the lens elements are mounted in the barrel and has nothing to do with the size of the image or image circle.

    In the case of this lens, the longer the Ff the better for me, as it is easier to focus at infinity with my 8x10 camera.

    Another way to look at it is a long Ff is like having a recessed lens board.
    125mm Fujinon.jpg
     
  9. Craig

    Craig Subscriber

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    What camera is your 8x10?
     
  10. locutus

    locutus Member

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    Thats, if i'm not mistaken, a Shenhao FCL810
     
  11. ic-racer

    ic-racer Member

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    Yes the Shen-Hao. Competitor to the Chamonix. A little heavier but it has front base tilt.
     
  12. jim10219

    jim10219 Member

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    A lot of wide angle lenses are retrofocal, which is the opposite of telefocal. It allows them to be compatible with more cameras.
     
  13. Dan Fromm

    Dan Fromm Member

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    Jim,
    True, but there are very few retrofocus w/a lenses for large format cameras. The 125/8 Fuji SW isn't one of them. You're probably thinking of w/a lenses for SLR cameras.

    About flange-focal distance. Lens design makes a difference. For example, the 105/3.7 Ektar, a heliar type, has a shorter ffd than the 101/4.5 Ektar, a tessar type. I've measured, and Graphic Graflex Photography, 10th edition says so too.

    As for design, the f/8 Fujinon SWs are very similar to f/8 Super Angulons. The 120/8 SA has ffd of 133.1 to 133.5 mm, depending on the shutter it is in. Scale that up by 125/120 and the range is 138.6 - 139.1.

    I vote for cold showers all 'round.
     
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  15. OP
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    Old-N-Feeble

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    You're too funny, Dan. Thanks for the info and the chuckle. :D
     
  16. Craig

    Craig Subscriber

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    Does it cover 8x10? The spec says it shouldn't.
     
  17. ic-racer

    ic-racer Member

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    The image circle is sharp right up to the cutoff, so one can crop it right up to edge of the circle. 125mm.jpg
     
    Last edited: Dec 22, 2017
  18. esearing

    esearing Member

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    Doesn't angle of view come into play here? The 3 Fujinon lenses mentioned have 76. 80, and 96 degree angles. My Schneider Xenar 135mm has 62 degrees @f22 but only a 161mm image circle which is small for 4x5.
    For 4x5 you only use 151mm, the extra image circle is acting as a zoom effectively turning your 125 into somewhere between 135 and 150.
    If you shoot both 5x7 and 4x5, owning the lens with the larger image circle would make sense.
    Ideally your lens kit should have similar angles of coverage so you get comparable values of the focal length.
    Example the Angulon lenses are between 81 and 85 degrees in focal lengths of 65, 90, 120, 165, and 210. The image circle grows larger due to focal length, lens to film distance.
    OR base your kit on image circle size for your format - example 200-210 mm @ f16 for 4x5.
     
  19. Nodda Duma

    Nodda Duma Subscriber

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    Sounds like the flange focal length is longer than the effective focal length. Not that unusual.
     
  20. E. von Hoegh

    E. von Hoegh Member

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    Extra image circle gives you room for movements, it does not make your lens act like a longer focal length.
     
  21. OP
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    Old-N-Feeble

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    Thanks everyone. The "effective focal length" is what slipped my failing brain. As others might suggest, I'm chasing a magic bullet. The 135mm focal length is neglected in large format. I was hoping to find a modern multicoated lens with an effective focal length of 135mm and plenty of coverage for 5x7 with movements.
     
  22. ic-racer

    ic-racer Member

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    Fuji_3_97_SW.jpg The angle of view of the print is related to how much you crop. By cropping off the corners with my 8x10 negatives I get an angle of view on the print as if I had a 135mm lens and printed full-frame. No reason you couldn't do the same with 5x7 format. You can always narrow your angle of view by cropping a wider lens, but you can't go the other way :wink:.

    For 5x7 format, I'd think this would be an awesome lens. Very sharp, multicoated, modern black rim shutter. The lens usually sells for much less than a German lens of similar performance. Mine has a small scratch in the rear element so it was only about $200.
     
    Last edited: Dec 23, 2017
  23. jim10219

    jim10219 Member

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    According to the diagram on IC Racer’s post, the front element is a negative meniscus lens, correct? That alone should suggest a retrofocal design. It may not be marketed as such, because you’re not gaining much distance over a standard lens design (less than 10%). But technically speaking, the fact that it’s flange focal length is slightly longer than its effective focal length, would mean it would have to be retrofocal, at least by definition. Or am I mistaken here?
     
  24. ic-racer

    ic-racer Member

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    Retrofocus lens design makes the Back Focal Length (distance from rear lens surface to the film plane) longer than the focal length. In the case of that lens, the Back Focal Length is 83.8mm and this is much shorter than 125mm.

    Again the Flange Focal length really has nothing to do with any of this, it is just the way the lens elements are mounted in the housing. A long or short Flange Focal distance does nothing to change the distance from the rear of the lens to the film.
    [​IMG]
     
    Last edited: Dec 23, 2017
  25. ic-racer

    ic-racer Member

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    Another interesting tangent is that retrofocus design is not exclusive to wide angle. For example 8mm Reflex Bolex needs a lens with a Back Focal distance around 17mm to clear the shutter and viewing mechanism. So, the 13mm lens (long for the diagonal of the format) is a retrofocus.
     
  26. OP
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    Old-N-Feeble

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    I'm a moron with regard to optical design. I guess I never took an interest in the subject. What I do wonder, is why Fuji opted for a retrofocus design, other than (maybe) an almost immeasurable decrease in fall-off at the corners... and/or (maybe) to allow infinity focus with cameras which have longer minimum spacing between lens and film plane.
     
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