'Splain to me Lucy.. Mamiya Floating Element Lens

Discussion in 'Medium Format Cameras and Accessories' started by k_jupiter, Dec 27, 2008.

  1. k_jupiter

    k_jupiter Member

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    Ok, after reading a number of threads about the floating elements in several Mamiya lens, I went back and looked at my collection. So that's what that ring does! Both 50mm and 65mm have floating elements. Now what does that do? It might explain why my 50mm shots have not been tack sharp. I have mostly used the 50 on 135 film that I run through a 220 back on modified spools. While I like the images a 36x68 negative give, they have not seemed that sharp. The 65 I shoot with a lot in 120 and haven't seen any image degradation, perhaps I was lucky and it's always been set on infinity?

    So what's the story? Why and how do you use this feature and does it truly help in sharpness issues with these lens?

    tim in san jose
     
    Last edited by a moderator: Dec 27, 2008
  2. Lopaka

    Lopaka Member

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    If you look at the floating element ring that rotates, directly opposite the distance scale on the rotating ring, there is what looks like a depth of field scale, with the widest apereture of the lens in the center. After you focus, you rotate the ring to point the distance on which you are focused at the center of the scale. After doing this, you re-check your focus. The theory behind this is that the floating element maximizes the sharpness of the lens for the specific distance on which you are focused. The bonus is, this scale also should give you an idea of the approx depth of field at that distance for various f-stops.

    Bob
     
  3. Alex Bishop-Thorpe

    Alex Bishop-Thorpe Member

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    Many lenses incorporate floating elements, but since a lot of them work on a focus helical (that dingus you twist to focus), it's adjusted for mechanically. Since we focus via bellows on the RB67, we have to adjust it manually...Which I totally overlooked the one time I borrowed the 50mm.
     
  4. David Brown

    David Brown Subscriber

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    Tim:

    Try the 50 on some 120 film and see if the negs are the same. I would suspect that the 35mm film might not be flat and/or exactly in the film plane with the setup you describe. Just a thought ...

    Also, try using the floating element on the 50. :tongue:
     
  5. keithwms

    keithwms Member

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    You *must* use the floating element on the 50 to have optimal corner sharpness! This will be especially obvious with the 6x8 back. It may not matter one iota for the 645 back.

    Unfortunately there is the confusion that several mamiya lenses have a ring that looks like a floating element adjuster but it's just a DOF ring.
     
  6. Lopaka

    Lopaka Member

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    Correct. Those that are floating element will have words like 'Floating System' on the ring.

    Bob
     
  7. k_jupiter

    k_jupiter Member

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    Hmmm, no "Floating System" on these lens, but when you move the ring, the lens elements turn inside. On each of my other rb67 lens (except the 150SF) there is a DOF ring that does nothing except give standard DOF info.


    tim
     
  8. keithwms

    keithwms Member

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    Tim, I think the rb ones don't necessarily have "floating element" inscribed on them. I have seen some that did and some that didn't. It's an unfortunate point of confusion that Mamiya brought upon their clients, and I suspect that it has led to some unfortunate reviews.

    Well, this is the [small] price you pay for bellows focusing instead of helicoidal. If the mamiya 6x7 systems were based on helicoidal then it'd be possible to have auto FE adjustment like you have in the Nikon wides ("CRC"). Oh well, one simply has to take the time to research and learn how to get the best performance.
     
  9. chriscrawfordphoto

    chriscrawfordphoto Member

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    What's funny is that Hasselblad's floating element lenses, the 40mm and 50mm FLE Distagons, have helical focusing but still have a second ring for the floating elements. A real pain, since the other manufacturers ho use helical focusing have the floating elements automatically adjust as you focus.
     
  10. Q.G.

    Q.G. Inactive

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    Not only other manufacturers. Other FLE lenses for Hasselblad have the floating element moved by the focussing helicoid too.
     
  11. chriscrawfordphoto

    chriscrawfordphoto Member

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    Which ones? The 40 and 50 are the only Hasselblad FLE lenses I know of. I'm talking about the 500 series cameras, not the focal plane shutter cameras.
     
  12. Q.G.

    Q.G. Inactive

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    A restriction! I see... :wink:

    But even with that restriction: the latest (and probably last) 40 mm Distagon has floating elements that are moved when you use the normal focussing ring.
     
  13. endneu913

    endneu913 Member

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    Holy thread revival!
    I figured ( again) that i would add to this info, instead of starting my own... I just picked up a 65mm KL for my RZ... a few questions:

    1) regarding the Floating system... actually regarding figuring out "focused distance" On a the longer lenses, ( like my 180) the Distance Scale on the camera body seems easy to understand, as the red and blue lines continue on underneath the the numerical values printed on the, making it easy to see which number they came closest to ( or so i thought! ) Now using the 65mm, the blue line for the 65mm lens comes nowhere near the numbers. This tells me i am doing something wrong here. But what.

    2) secondly, i assume when using the RB lens on the RZ body, the shutter speed ring on the lens itself over-rides the shutter speed knob on the RZ body? Seems thats the case anyway. ?

    3) i assume adjustments of the floating lens ring are invisible thru the finder.... much like depth of field being invisible to the finder, but real on the film nonetheless.... correct?

    Thanks!

    - Grae
     
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  15. endneu913

    endneu913 Member

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    no one wanna take a crack at this? ... ^
     
  16. konakoa

    konakoa Member

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    Grae,

    1.) What's probably throwing you off is that you're using an RB lens on a RZ camera. RB lenses require a bit more focus extension on the RZ camera to reach infinity focus. As the chart on the side of the camera is figured for RZ lenses, it won't match up with a RB lens.

    2.) Yes -- the RB lenses are completely mechanical, and have no electrical contacts with the RZ body. The shutter speed dial on the RZ won't do a thing because there is no way for it to control a RB lens. It's best to set the dial on the camera to "RBL" (if I remember right this turns off the body/lens electronics) when you have a RB lens on the RZ.

    3.) I've never been able to see the floating lens adjustments on my 65mm while looking through the camera, but I can tell you they do show up on the film!
     
  17. endneu913

    endneu913 Member

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    Danny, thanks! that helps a ton.... so i will have to guess on my distances i assume.
     
  18. david_mizen

    david_mizen Member

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    do i take it to mean that ALL Mamiya rb67 50mm and 65mm lenses use the floating element design irrespective of whether they are non c or c series ?
     
  19. John Koehrer

    John Koehrer Subscriber

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    If you look closely while adjusting the element the focus shift is visible. Watch the background. It's sorta like the Nikor 135mm SF
     
  20. fotoroberto

    fotoroberto Member

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    Well, as You can see, there is a shutter and aperture mechanism between helical mount and FLE, so it would be quite difficult to implement synchronized control of the FLE correction on those lenses...

    With a little practice it becomes natural to adjust correction and then focus the image
     
  21. Q.G.

    Q.G. Inactive

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    And with a little practice also, Zeiss managed to put a 'linked' FLE and shutter assembly in a helicoid focussing lens too. See the latest incarnation of their Hasselblad 40 mm Distagon. :wink:
     
  22. Q.G.

    Q.G. Inactive

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    I just see i said just about the same thing in december 2008!
     
  23. Voyager13b

    Voyager13b Member

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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....
     
  24. Q.G.

    Q.G. Inactive

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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. :wink:
     
  25. Rudeofus

    Rudeofus Subscriber

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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.
     
  26. Q.G.

    Q.G. Inactive

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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).