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Thread: Help understanding Telephoto lenses

  1. #1

    Join Date
    Dec 2019
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    219

    Help understanding Telephoto lenses

    Hi all. Iím starting to give up on searching the forum for information because it just turns up more questions!! So, let me just ask this one here....

    Iím trying to understand the requirements for a camera and user when the lens has a ďTĒ in the name. Iím looking specifically at the Nikon Nikkor 360mm f/8 T ED with 500mm f/11 convertible lens.

    As I understand it, a 150mm standard lens (as an example) will need 150mm of bellows extension. Same with a 210mm...but I seem to remember that the rules change when you stick a ďTĒ in the name. Is that right?

    How long do my bellows need to go to use a 360mm lens like that Nikon? What about the 500mm version?

    Do the telephoto type lenses require anything special about the camera setup or ability? How about the bellows?

    What Iím also getting at is this...I know Iíd like the 360mm focal length and I figured Iíd jump over 300mm and use 360mm at the top end. But, if the 360 is hard to use or has any other funk aspects to it, maybe I should blow off the 360.

    Itís akin to this...the 75mm vs 90mm comparison. Both are nice, but the 75mm is definitely more of a pain in the ass to use whereas the 90mm is very straight forward. Is there anything going on at the top end with the 300 and 360?

    So can you guide me on understanding pros/cons, special needs, certain talents required for the 360mm or is it pretty simple? And if I did go that way, is the 500mm easy to use or is there anything funky going on with that one?

    Thx!!!
    Anything in life worth having is worth sharing.

  2. #2

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    Hampton, VA
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    Re: Help understanding Telephoto lenses

    Adam,

    No special talents required...

    Telephotos need less belows extension than the indicated focal length. The Nikon 360 tele requires roughly 260mm extension (for infinity focus) while the 500 tele requires about 350mm extension. That is their principal advantage.

    FYI the Ebony camera company used to have a great table for lens parameters, but they are no longer in business and the web page is gone. Fortunately a UK group grabbed the info and it is available at https://www.5x4.co.uk/pages/Lens-Table/. The parameter of interest in the case is the last column, "Flange back"

    I've got the 360-500-720 set and use it quite a bit. The three focal lengths share the same front elements (and shutter) - you simply unscrew the rear element for the 360 and replace it with the 500 rear element, or the 720 rear element. The complete set comes up for sale only rarely - you will likely have to piece it together over time.

    Hope this helps. Lets see how long before this thread goes way off the rails

    Bob

  3. #3
    Huub
    Join Date
    Dec 2013
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    Netherlands
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    Re: Help understanding Telephoto lenses

    The main price you pay when using telephoto's is that front tilt gets difficult. Where the front nodal point of most lenses is more or less in the center where the shutter is, with telephoto lenses it is way in front. So when you start tilting the lens, you get all sorts of odd effects and focussing can become a pain. I don't know you camera, but having a good set of back movements helps a lot when using this lens. There is an older threat on telephote lenses that explains it all in detail.

  4. #4

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    Dec 2017
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    Re: Help understanding Telephoto lenses

    I also think the aforementioned Nikkor is great. I would love to have one of those. Especially for mountain shots. I think most of the time there is too much in the pictures. A long focal length is the solution.

    On my Technika I can attach a 420mm Apo Ronar at most, because of the bellows extension. A tele would be better. There is also a very good 600mm Fujinon T. But that is also expensive. And you have problems with the tilt.

    A solution would be to use roll film in 6x7 or 6x9, with a roll film holder. That way the image detail is narrower. Anyway, you magnify distant views less than close-up views with short focal lengths, which offer more immersion because of the imaged ground. It is a difference like between van Eyck, Breughel or Rogier (short focal length) and Giotto, Piero della Francesca, Massaccio (long focal length). Alternatively, you can enlarge good sections from 4x5.

  5. #5

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    Palo Alto, CA, USA
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    Re: Help understanding Telephoto lenses

    https://www.largeformatphotography.info/lenses/
    The Nikkor T lenses are heavier, a little harder to use with tilts, have more restrictions on shift, but are a good way to get a long focal length on a 4x5. The Fujinon T lenses are also good and are similar but donít share a common front lens group.

    Iíve been happy with my Fujinon T 600 and because of the long focal length, donít normally use any movements. Weight is the only drawback in use for me.

  6. #6

    Join Date
    Jul 2008
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    2,017

    Re: Help understanding Telephoto lenses

    Recently discussed.... LOTs.
    https://www.largeformatphotography.i...-film-how-good

    About zero has changed since the introduction of "telephoto design" LF lenses to this day. Essentially, they are intended for field folders that do not have enough camera extension and bellows draw for longer focal length lenses, or to compensate for a camera limitation.

    Optically, most non-telephoto lenses have (APO process lenses aka APO nikkor APO artar, APO ronar and etc) better performance except they demand the camera being able to support them with enough extension and bellows length and if the lens is in barrel, a shutter..
    Exceptions to this might be the last generation of Schneider APO tele xenar lenses (not tried then due to lack of interest and lots of $ for what they are). The need for shutter with lens is a very real and limiting factor and reality for many LF cameras.


    Bernice

  7. #7

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    Re: Help understanding Telephoto lenses

    Quote Originally Posted by AdamD View Post
    Hi all. I’m starting to give up on searching the forum for information because it just turns up more questions!! So, let me just ask this one here....
    You need this book:

    https://www.abebooks.com/servlet/Boo...-srp1-_-title1

    https://www.abebooks.com/servlet/Boo...%26sortby%3D17

  8. #8

    Join Date
    Jul 2008
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    Re: Help understanding Telephoto lenses

    Or this book by Steve Simmons:

    https://www.amazon.com/Using-View-Ca.../dp/1626540772


    Bernice

  9. #9

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    Sarnia, Ontario, Canada
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    Re: Help understanding Telephoto lenses

    Adam,

    Not mentioned thus far is the use of a "top hat" style lens board that has an extension built into the lens board, moving the lens away from the front standard.

    It too does the same funky stuff on the front tilt, but you get the optical performance of a standard lens design, versus a telephoto lens design. In fact thinking of a lens mounted well in front of the front standard is a good way to visualize the impact of front tilt when using a telephoto lens or a lens mounted on a top hat lens board.

    Just another solution with its own compromises,

    Len
    Last edited by Len Middleton; 27-Jan-2021 at 14:33.

  10. #10

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    Re: Help understanding Telephoto lenses

    Hello from France!

    I have uploaded (see below) a diagram explaining how a telephoto works, not a Nikon but a Schneider-Kreuznach "360 mm" (actually f = 353 mm) Tele-Arton.

    For this lens, the flange-focal distance is only 210 mm. That is to say you only need about 210 mm of bellows draw to focus at infinity.
    With a 360 mm plasmat type lens or apo-repro (symmetrical) type you would need about 360 mm.

    Click image for larger version. 

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    However any additional extension required to focus on a object located ... ahem "much closer than infinity" requires exactly the same amount of additional extension, whichever the lens formula (of same focal length) might be.
    In other terms, with a telephoto you have a gain in bellows draw at infinity, but no additional gain for real-world-objects not located at infinity.

    Regarding tilting this kind of lens, well, nothing really mysterious.
    The rear nodal point H' = N' is not "at rear" but located (in this particular lens design) about 143 mm in front of the lens board: 210 mm + 143 mm = 353 mm = focal length.
    Depending on where your axis tilts are located on your front standard, for sure, when tilting the telephoto lens, the image will move much more and will probably defocus much quickly than with a plasmat or a symmetrical design where the rear nodal point is close to the center of the lens board. But if you have base tilts, anyway you never rotate around the rear nodal point of any of your lenses!
    Once you know where H'=N' is located, i.e. exactly one focal length ahead of the focal plane (this is a general rule valid for all lenses!), you can anticipate what will happen when you tilt the lens.

    My understanding is that photographers in the good old days who worked with this kind of telephoto view camera lens hardly ever tilt them. So where is the problem?

    And just for fun, imagine that you plan to make panoramic stitching with this lens.
    The diagram shows where the entrance pupil is located i.e. not far from the lens board, at a short distance behind. So you should rotate the camera as a whole for panoramic stitching around the entrance pupil like with any lens, and certainly not around the rear nodal point (this point N'=H' is irrelevant to parallax effects, hence irrelevant to panoramic stitching), located in air in front of the lens quite far away!
    The entrance pupil, like in any lens, is neither the object nodal point H=N nor the image nodal point H'=N', but this has been well-known to our all readers from a long time

    A copy of this jpeg diagram can be also downloaded from here.

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