will Nikon release professional "digial" lenses ?

Discussion in 'Nikon' started by Michael Schnell, May 25, 2006.

  1. If I understand this correctly, the result of this discussion is that
    special "DX" lenses don't make sense in the Tele area, but with
    something link 28mm we maybe will see more of them.

    -Michael
     
    Michael Schnell, May 27, 2006
    #81
    1. Advertisements

  2. You are talking about the 105mm f/2.8G ED-IF AF-S VR Micro-Nikkor just
    This discussion showed, that dedicated "DX" lenses don't make sense for
    Tele, and maybe this area starts at some 100mm.

    -Michael
     
    Michael Schnell, May 27, 2006
    #82
    1. Advertisements

  3. Michael Schnell

    J. Clarke Guest

    Is that the _only_ reason?
     
    J. Clarke, May 27, 2006
    #83
  4. Michael Schnell

    Stacey Guest


    Probably only for lenses below 40mm as this length would "natively" cover
    full frame 35mm without any fancy optical tricks.
     
    Stacey, May 27, 2006
    #84
  5. Michael Schnell

    bjw Guest

    Hey, I said "at least in part." How many weasel words do
    you want? Other things could affect it, but I don't think the
    relative location of entrance pupil and iris has much to do
    with bokeh.

    When a lens is _completely_ out of focus, a point source is
    imaged as something that looks like the entrance pupil
    (this is why mirror lenses give donut shaped blur). In normal
    photography, you're usually not that far out of focus, so the
    images are somewhere between good-focus and circular.
    Different lenses will make this transition differently.

    You can think of the out of focus image as what the cone
    of rays looks like when you put the sensor a few mm ahead
    or behind of the plane of focus. For spherical aberration,
    different parts of the lens converge ahead or behind of
    some compromise focus. See Figure 1 at
    <http://www.vanwalree.com/optics/spherical.html>

    In typical photographic use of limited DOF, the background
    is out of focus. This means the lens is farther from the
    sensor, so it's as if the sensor were at position "c" in
    that Figure 1. The effect is that the blur pattern is bright
    in the center and dim at the edges, which is usually
    considered pleasing bokeh. However, for overcorrected
    spherical aberration, it's the opposite effect and you can
    get a blur pattern which is brighter at the edges, which
    many people do not like - it can produce "double-line"
    bokeh.

    There is a good comparison of over and under corrected
    spherical aberration at
    <http://en.wikipedia.org/wiki/Spherical_aberration>
    See the first picture, which is
    <http://en.wikipedia.org/wiki/Image:Spherical-aberration-disk.jpg>
    Keep in mind these are idealized simulations.
    The rightmost column is beyond the focus point,
    which is what happens to the background. Top row
    is over corrected (note the bright ring), bottom row is
    under corrected.

    There is also a discussion of spherical aberration, with
    some real out-of-focus images from a camera lens, at
    <http://www.vanwalree.com/optics/spherical.html>
    These pages describe it better than I can, because
    pictures really help.

    Personally I feel that bokeh is interesting, but also
    that bokeh is sometimes abused to provoke equipment
    flamewars, much as sharpness has been. Cynically
    I think people started flaming each other about bokeh
    once they realized sharpness was not as good for
    flamebait, since all the major OEM manufacturers make
    pretty sharp lenses once you get beyond the absolute
    cheapo stage.

    Ben
     
    bjw, May 27, 2006
    #85
  6. Exactly right, Stacey. Now if you can just get straightened out about the
    "art" business you'll be all set. ;-)
     
    John Falstaff, May 27, 2006
    #86
  7. Michael Schnell

    Stacey Guest

    I suppose it can be, but for me bokeh can make or break a lens. I just tried
    a tamron SP 400mm F4 and while nice and sharp, the bokeh was pretty nasty
    and ruined the lens's ability to achieve good selective focus, even wide
    open. I exchanged it for a nikon 300mm F2.8 and the difference in bokeh
    (even with a 1.4X converter) is like night and day even though the tamron
    was just as sharp. I found the same to be true with the olympus ZD 14-45 vs
    the 14-54, the main advantage to me is the smoother bokeh the 14-54 has.

    I also don't buy the "lenses with good bokeh aren't as sharp" line some
    people try to pitch, that just isn't true. This is a test shot of my 18
    year old basset hound I shot this morning trying out the nikon 300mm f2.8
    on my olympus E1, looks plenty sharp wide open and the background is creamy
    smooth. I've found the 180mm F2.8 sonnar to be the same way.

    http://img.villagephotos.com/p/2005-1/937049/toby.jpg

    I think trying to get a lens that's sharp wide open and still have nice
    bokeh is one of the hardest things to accomplish.
     
    Stacey, May 27, 2006
    #87
  8. Michael Schnell

    bjw Guest

    It's correct, but you make it sound too complicated.
    You don't need to know the optical design of the lens
    to understand the entrance pupil. The entrance pupil
    is the image of the iris as viewed from the front of the
    lens. If you hold a lens up to the light and put a ruler
    in front of it, you can measure the pupil diameter
    (apart from small parallax effects because the pupil
    isn't exactly at the same place as the ruler). Try it
    with a 50mm lens.
     
    bjw, May 28, 2006
    #88
  9. Michael Schnell

    Stacey Guest


    Stalking are we?
     
    Stacey, May 28, 2006
    #89
  10. Michael Schnell

    DoN. Nichols Guest

    [ ... ]
    Well ... *my* enlargers had multiple lens boards which could be
    interchanged, allowing larger enlargements from smaller negatives
    without having to make the column excessively long.

    However -- what I think that he meant here was to vary the focus
    adjustment (the distance from the negative to the lens) which does vary
    other factors in the process.

    Enjoy,
    DoN.
     
    DoN. Nichols, May 28, 2006
    #90
  11. Michael Schnell

    DoN. Nichols Guest

    Add to that the smaller market, because there are no other
    cameras on which it can be used (without modification), which means that
    the custom design is amortized over a much smaller probable sales.

    Enjoy,
    DoN.
     
    DoN. Nichols, May 28, 2006
    #91
  12. Michael Schnell

    DoN. Nichols Guest

    Perhaps so, perhaps not. I don't have an example of that lens,
    but most long focal length lenses for 35mm are designed with a negative
    lens grouping near the mount so it winds up with a shorter physical
    length than the focal length would otherwise require. That negative
    lens grouping will probably be the limiting factor on larger format
    coverage.
    He said *mount* diameter, and that *can* be smaller for a given
    lens design without vignetting when covering a smaller sensor. But
    Nikon apparently has no reason to abandon the older lens mount design,
    for which *I* am personally thankful.

    Enjoy,
    DoN.
     
    DoN. Nichols, May 28, 2006
    #92
  13. Michael Schnell

    Paul Furman Guest


    I think so. Maybe more benefit in zooms than fixed though?
     
    Paul Furman, May 29, 2006
    #93
    1. Advertisements

Ask a Question

Want to reply to this thread or ask your own question?

You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.