will Nikon release professional "digial" lenses ?

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

  1. Michael Schnell

    Stacey Guest

    Stacey, May 27, 2006
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  2. Michael Schnell

    Stacey Guest

    Stacey, May 27, 2006
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  3. Michael Schnell

    Stacey Guest

    A real one is the 4/3 olympus 300 f2.8 gives the equiv of a 600 f2.8. Notice
    it's the same size as a 35mm format 300 f2.8 but is much smaller than a
    600mm f2.8 would be. What you have to look at is the field of view vs lens
    speed. That's what makes a DX or a 4/3 tele lens smaller.
    Stacey, May 27, 2006
  4. Michael Schnell

    Stacey Guest

    Except in the dark room example you moved the distance between the lens,
    paper -and- negative which also changed the FOV. If you just changed to a
    smaller size paper, the light output wouldn't change which is what a
    smaller digital sensor is doing. I did this regularly in the darkroom to
    test exposure, remember doing test strips? :)
    Stacey, May 27, 2006
  5. I guess (but I am not a lens designer) that when you move the iris closer to
    the entrance pupil that the effects of diffraction will be bigger.
    Philip Homburg, May 27, 2006
  6. You are confusion a number of things. For of all, a 300/2.8 on 4/3 is
    equivalent 600/5.6 on 35mm. This holds for both the low light performance
    (number of photons per solid angle) and the for DoF. Of course, due
    to engineering differences, the sensor in the 4/3 camera may have a low
    light performance that is better than 2 times worse than 35mm, but that
    doesn't have anything to do with the lens.

    I can easily convert a 300/2.8 to a 600/5.6 by simply adding a 2x

    The other thing is that OP already knew that a 300/2.8 on DX is equivalent
    to a 450 of 35mm, but still he assumed that making a DX version of the 300/2.8
    would provide additional benefits.

    Of course, to find out whether the olympus 300 is really worth its
    money, you would have to compare it to for example a 600mm lens on a full
    frame 35mm body, to a Nikkor 500/4 on a D2X (or D200 depending).
    Philip Homburg, May 27, 2006
  7. Michael Schnell

    J. Clarke Guest

    So let's see, if you take that lens and put it on a 35mm and crop out 3/4 of
    the frame then you have somehow turned it into an f/5.6 lens? Do you see
    how silly that looks?

    What makes it the "equivalent" of a 600 is that the 4/3 system has a sensor
    1/4 the size of a 35mm frame (half in each dimension). The aperture is
    The number of photons per solid angle is the same for that lens if you put
    it on a 35mm, an APS-C, a 4/3, or a 8x10. What changes is the angle
    subtended by the sensor.
    No, it doesn't.
    Yes, you can, but that is not how a DSLR works.
    If one needs an f/2.8 lens then comparing to an f/4 is irrelevant.
    J. Clarke, May 27, 2006
  8. Michael Schnell

    J. Clarke Guest

    You may have a zoom on _your_ enlarger but all of them that I've used have
    had fixed focal length lenses. You can vary the print size by adjusting
    the lens-to-film distance and the height of the head but that doesn't
    involve changing the focal length.
    J. Clarke, May 27, 2006
  9. Michael Schnell

    J. Clarke Guest

    The distance from the entrance pupil doesn't necessarily enter into it with
    multielement lenses. But I believe you are correct in your assessment and
    find myself wondering if this is one of the reasons that different lenses
    of the same focal length show different bokeh characteristics.
    J. Clarke, May 27, 2006
  10. No I don't see how silly that looks. Images of the same subject can be
    considered equivalent when they have equivalent field of view (and
    perspective), when sharpness/resolution correspond, when noise/grain
    corresponds, and when DoF is the same.

    If you crop a 4/3 frame out of a 35mm frame, you lose resolution and the
    field of view is different.

    So, a 300mm on 35mm and a 300mm on 4/3 will never give equivalent images
    independent of the aperture.
    What makes the 600/5.6 on 35mm equivalent to 300/2.8 on 4/3 is that the
    resulting images correspond in all the parameters I listed above.
    Yes, solid angle was the wrong word. Though the solid angle as seen from the
    subject towards the camera is the same.

    What I meant was the number of photons per constant fraction of the frame.
    One doesn't need an f/2.8 lens. One needs either a specific DoF (which
    requires an aperture that depends on the frame size) or a specific low noise
    performance, which requires an aperture that depends on both the frame size
    and the sensor technology.

    Absent differences in technology, the required aperture varies with frame size.

    That is no way that the effects off f/2.8 on 8x10" large format is equivalent
    to f/2.8 on a sub-miniature P&S.
    Philip Homburg, May 27, 2006
  11. Michael Schnell

    Father Kodak Guest

    Ooops. Good catch. You're right. I meant to say, "It's not a DX
    lens." Thanks for this correction.

    Father Kodak
    Father Kodak, May 27, 2006
  12. You don't need a DX lens at all.
    I see. That seems to be the final clue of the discussion (regarding Tele

    Michael Schnell, May 27, 2006
  13. Michael Schnell

    J. Clarke Guest

    No, you don't. You don't change the resolution of a recorded image with a
    pair of scissors.
    Yes, it is, that's the whole point.
    Nobody claimed that they would. Any given lens on any given format will
    never give equivalent images to any lens on any other format if by
    "equivalent image" you mean full frame.
    Since sensor technology at any given time is pretty much fixed, this point
    is pretty much moot. If you have a good enough sensor you can shoot black
    cats in coal bins at midnight at F/128, but we don't have that much
    variation in sensor performance among the various interchangeable lens
    digital formats.
    There is no such thing as parity between formats. You always give something
    up to get something. You seem to think that the primary function of
    aperture is to control depth of field, others do not. To each his own.
    J. Clarke, May 27, 2006
  14. Michael Schnell

    w.beckley Guest

    Thank you Ben (and Jeremy) for the explanations here.

    Just to clarify, aperture ratio is focal length divided by the size of
    the entrance pupil, and the entrance pupil is not a component with a
    mechanically physical size, but rather a somewhat virtual thing (that
    can be measured absolutely) determined by a number of factors, primary
    of which would be front element diameter and physical iris opening
    diameter (but also taking into account numerous factors of optical
    design, like elements and element groupings).

    Is that a servicable way to look at it?


    w.beckley, May 27, 2006
  15. Michael Schnell

    J. Clarke Guest

    You're overthinking it to the point that perhaps if you have calculus and
    linear algebra you might want to pick up a university optics text aimed at
    physics majors and work through it. Trouble is that that won't really help
    you take better pictures.
    J. Clarke, May 27, 2006
  16. No, it's not "exactly the same thing." It's entirely different.

    With an enlarger you are indeed spreading the same amount of light over a
    larger area, requiring longer exposure for the same f-stop. But no such
    thing is happening when you use a lens designed for full frame on a smaller
    than full-frame sensor.

    Go back to your enlarger analogy and imagine everything set up to make an
    8x10 print. Now without changing anything at the enlarger itself, you
    replace the 8x10 easel with a 5x7 easel. The exposure doesn't change; you're
    just printing a smaller part of the original image. That's exactly analogous
    to using a smaller sensor with a lens designed for 35mm full frame.
    John Falstaff, May 27, 2006
  17. I'll have one of those too, please.
    John Falstaff, May 27, 2006
  18. At that focal length I don't think there's any reason to make a lens
    specifically DX, even when the manufacturer accepts that 35mm is nearly
    John Falstaff, May 27, 2006
  19. Michael Schnell

    bjw Guest

    Different lenses have different "bokeh" characteristics
    at least in part because they have different amounts
    of over/under corrected spherical aberration.
    bjw, May 27, 2006
  20. Michael Schnell

    bjw Guest

    I guess I don't know what you mean by "how much
    diffracted light is in an image as a percentage of
    total light." Formally speaking, all the light is diffracted.
    Are you thinking of the edges of the aperture as being
    solely responsible for the diffraction? That's not really
    what happens.

    In terms of calculating the size of the diffraction-limited
    spot, it's the overall f-number that matters, not the physical
    size of the iris, so it's better to think of the entrance pupil
    than the iris.

    To give a little more detail, if the lens were perfect, on a
    point source it would produce a diffraction pattern that is
    the (square of the) Fourier transform of the entrance pupil.
    For a perfect circular aperture, the pattern is an Airy function
    (named after George Airy). The diameter of the aperture
    is inversely proportional to the size of the Airy spot, and
    the fact that the aperture has sharp edges leads to a
    high-frequency ringing pattern as a function of radius.
    In real use of a real lens, aberrations, imperfections,
    and non-monochromatic light smooth out the ringing

    In general, sharp features like edges in the aperture or pupil
    produce high-frequency patterns in the diffraction pattern.
    Another example is the diffraction spike pattern seen in
    telescope images of bright stars. This is caused by the
    spider that holds the secondary. For a four-arm spider
    you see a cross pattern of spikes, for a three-arm spider
    you see six spikes.
    bjw, May 27, 2006
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