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  1. #21

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    I just see i said just about the same thing in december 2008!

  2. #22

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    I'm not sure about the floating element distinction on the RB lenses, but the RZ lenses with floating elements carry the "L" designation, and instead of having a DOF calculator that spins 360 degrees to show imperial or metric scales, it has just the floating element ring, which does double duty. Anyway, that has all been noted here already, but I wanted to offer that my experience with the non-floating element 65 when I used one owned by work, and the later L-A version with the floating element has been that proper use of the floating element makes a noticeable difference in sharpness and reduced image distortion across the field, and has an especially noticeable effect in field flatness towards the corners when shallow DOF is in play. The premium is not that high on the used market, and is well worth it.

    The last thing to consider is that the price we pay by having to manually set the floating element is more than made up by the fact that our bellows focused lenses do not suffer from the design compromise of being forced to optimize a lens for near or far focus at the drawing board. I remember this discussion several decades ago at a large format workshop that I attended, but it slipped into history over the years until I was reminded of the issue on the Hasselblad site a few days ago.

    Hasselblad wrote a detailed paper on the reason they dropped Zeiss as a lens making partner, and went with Fuji for their H series lenses. They honored their long relationship with Zeiss, but explained that Zeiss made lenses for Hasselblad without allowing much in the way of direct development involvement from Hasselblad engineers. The result was that Zeiss lenses were provided with Zeiss built shutters, and designs were optimized at infinity focus. That was simply how Zeiss did things, take it or leave it (that's a paraphrase).

    Fuji, on the other hand, was eager to do the team design thing, and had the computer software to allow the teams to be half a world apart. The end result is that the new H series lenses sport Hasselblad designed and built electronic shutters, and Fuji glass and barrels that are assembled at Fuji around complete Hasselblad shutter/iris assemblies shipped from Sweden. Pretty slick, no? It gets better, and this is the forgotten point....

    The new Hasselblad lenses are also helical focused lenses as in the past. This is a big space saver, as the focus is made by moving lens elements, and does not require as much motion as with bellow systems (how well us RB/RZ users know that). The downside is that helical focus lenses cannot be completely corrected for aberrations at all focus settings, as lens element groups are moved to to achieve focus, and that changes the corrections needed. So, a choice must be made. Near focus correction, or infinity focus correction? Zeiss chose infinity focus optimization, and according to the charts posted by Hasselblad, that gave stellar performance at infinity, but lesser, and sometimes downright low grade performance at closer focus ranges.

    Their thought was that most people using their gear are shooting closer than at infinity, as they are shooting portraits, studio, product, interiors, etc. When they partnered with Fuji, they optimized the H series lens designs for close work, did the best they could do within reason for infinity, and corrected what errors remained at infinity with digital software. Obviously, it was a huge success. What surprised me most though, was how those awesome Zeiss lenses that set the standard at infinity really suffered at closer ranges.

    That reminded me that our "old school" bellows-focused lenses do not suffer anywhere as much from having to choose near or infinity optimization at design time, as the main elements are fixed, and do not introduce additional errors to the mix as they are focused. If the lens is a well corrected design, it remains that way (for the most part) across the board. The floating element corrects for flatness of field errors, and had to be moved to accommodate the change in the angular nature of the light rays making it to the film or sensor plane as it's point of focus changes from infinity to close up. It's a much easier problem to design a single moving corrective element that isn't even critical in terms of positioning than to design a complex cam arrangement to move several elements in critical step though, and still have to accept compromise in the end.

    That's not to say that our bellows lenses are perfect by any stretch, but the odd little routine we go through to focus our subject does have it's benefits....

  3. #23

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    You're forgetting one thing though.
    Using helicoid focussing does not necessarily also mean internal focussing. Most helicoid focussing lenses (those made by Zeiss for Hassselblad too) use unit focussing, just like RB/RZ lenses. No difference.

    You're forgetting one other thing too.
    When moving the entire lens, to change focus from near to far (or vice versa), you do not have an opportunity to change correction. Using internal (or group) focussing (or at least a floating element or group, whether used for focussing or not), you do.
    So your "old school" bellows focussed lenses actually do suffer more from having to choose between near or infinity optimisation. Just because the elements are fixed.

    Though you were correct in the beginning of your post, in the end you got it entirely backwards.

  4. #24
    Rudeofus's Avatar
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    Just to back up Q.G. on this: a guy in a german forum ran a simulation of a 35mm format fully corrected 50/1.8 with and without extension rings. The results with the extension ring were downright depressing (field curvature, chromatic aberrations). Lenses are mostly corrected for infinity focus, where incident light rays are nearly parallel. As you focus closer, these light rays are no longer parallel and the correction is way off.

    Even Mamiya seems to be aware of this, since they market a 140mm macro lens with is supposedly optimized for close range.

  5. #25

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    The main point however is that floating groups/elements/internal focussing provides a way to make a lens less scale sensitive. Not the opposite.

    Though with many lenses not really a big problem, unit focussing lenses can't throw anything in the way of changing conjugated distances. They are what they are, and if that doesn't suit the changed conditions, too bad.
    Lenses with floating elements, and the modern 'floating everything' IF lenses, adapt to changing circumstances the moment the change occurs.

    If it were a contest, that way of focussing would win hands down over bellows or unit focussing lenses.
    But there is another big "if": if that constantly changing optical design is used to indeed keep correction at a high level, and not just to make a lens cheaper to make (front cell focussing), of faster to (auto-)focus (less weight to shift fast when all you have to move is a couple of elements).

  6. #26
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    I found this thread and have and need some help too.
    My RB67, 65mm Sekor "C" lens arrived yesterday. It appears to be a "floating element" lens. When I bought it off of ebay there was no mention of a "floating element". The lens is in9 out of 10 condition and everything appears to be working fine. My question is about the floating element adjustment too.
    There is a ring closest to the end of the lens that has distance in ft/m. at the two ends of adjustment travel there are detents that feel just like aperture "clicks". When I rotate this ring I can see that the inside of the lens is turning but nothing on the outside is moving.
    When I look through the viewfinder, after focusing like normal, I turn the "floating element" ring but can tell not any difference in sharpness or anything else for that matter. Where do I find the distance to use to adjust this element? the scale on the side of the bellows???
    How do I use this lens properly???
    Does the floating element really make a difference in the quality of the photo or is it a gimmick? I am a real lover of my RB67 system and understand most of the features but this one is a bit confusing...
    "Generalizations are made because they are generally true"
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    Barry
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  7. #27

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    I'm not quite sure, but believe the thing to do is focus the lens normally, read the distance from the normal scale on the side of the camera, set the FLE ring accordingly, and then refocus.

    Generally, floating elements do indeed make a difference, yes.

  8. #28
    stradibarrius's Avatar
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    I hope that is not how this works!!! If so it seems like a real pain....I am afraid your are correct though.
    "Generalizations are made because they are generally true"
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    Barry
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  9. #29
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    Quote Originally Posted by Q.G. View Post
    I'm not quite sure, but believe the thing to do is focus the lens normally, read the distance from the normal scale on the side of the camera, set the FLE ring accordingly, and then refocus.

    Generally, floating elements do indeed make a difference, yes.
    I have a 50mm floating element C lens. There is no need to refocus after you set the FLE ring.

    The ring doesn't change the focus on the lens. As I understand it, it changes how the lens corrects for aberrations and/or field curvature.

    Usually I don't bother to read the distance off the camera side scale. I just estimate the distance and set it.

    The detents are there because if you are working quickly, you can just set the ring to either the close detent, or the far detent (whichever is applicable to your subject) and the floating element correction will be very close to being optimum.
    Matt

    “Photography is a complex and fluid medium, and its many factors are not applied in simple sequence. Rather, the process may be likened to the art of the juggler in keeping many balls in the air at one time!”

    Ansel Adams, from the introduction to The Negative - The New Ansel Adams Photography Series / Book 2

  10. #30
    stradibarrius's Avatar
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    So the floating adjustment is not critical like normal focus? If it is close it is good?
    "Generalizations are made because they are generally true"
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    website: http://www.dudleyviolins.com
    Barry
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