New 50mm Lens From Nikon

Discussion in 'Nikon' started by Manzoorul Hassan, Jan 17, 2008.

  1. Manzoorul  Hassan

    Mr.T Guest

    Then maybe you can stop all the pro Nikon-Anti Canon posts and give the rest
    of us a break!
    Good for you. Maybe you should move on to the business of just taking
    photo's with them now then :)

    MrT.
     
    Mr.T, Jan 28, 2008
    1. Advertisements

  2. The distance of the final element is irrelevant, what matters is the
    distance of the centre of focus. That's what effects how one degree of
    wobble in camera direction translates into lateral movement of the
    image across the sensor.
     
    Chris Malcolm, Jan 28, 2008
    1. Advertisements

  3. Rita wouldn't get it.
    I estimate LV-15 or thereabouts.
    Unless Reason is the name of a new Nikon DSLR.

    -Wolfgang
     
    Wolfgang Weisselberg, Jan 28, 2008
  4. I am and I'm enjoying the hell out of them.





    Rita
     
    Rita Berkowitz, Jan 28, 2008
  5. Not for in-camera IS/VR. A simple analogy is teeter-totter (fulcrum). Take
    a long lens for instance, 400-600mm, have their final element much further
    away form the sensor plane than say a 50mm. This final element is like a
    fulcrum and on longer lenses passes a much higher degree of movement across
    the sensor. The sensor must work harder, faster, and move farther to
    neutralize this movement. This is why in-camera stabilization is
    impractical for long lenses.





    Rita
     
    Rita Berkowitz, Jan 28, 2008
  6. Where the rearmost element is makes no difference that I can see. The
    greater the focal length the greater the image movement at the focal plane.
    It must be directly proportional to the magnification.

    Neil
     
    Neil Harrington, Jan 28, 2008
  7. Why should the final element be "like a fulcrum"?

    I think in-body stabilization probably is *not* as effective as in-lens in
    the case of long lenses, but not for that reason.

    Here's a thought experiment for you: Consider an SLR with any old familar
    135mm telephoto. The rearmost element is typically far back, close to the
    lens mount. Now consider an identical SLR, but with a 135mm press camera
    lens mounted on a bellows or something. Obviously its rear element will be
    much farther forward.

    According to your notion these two arrangements must behave entirely
    differently in image wobble at the focal plane, right? But I don't see how
    they can. Both will have the same image at the focal plane when in the same
    place and pointed in the same direction. Turn them both through some
    identical small angle and their images will still be the same. So any image
    wobble at the focal plane of one must be exactly the same as image wobble in
    the other. There isn't any "fulcrum" determined by rear element location.

    Neil
     
    Neil Harrington, Jan 28, 2008
  8. Well, you've just changed the optical formula to do the same thing except
    for the final real element to make correction of light going to the sensor
    plane. Both lenses will behave differently while theoretically shining the
    same image on the sensor. The lens with the element closer to the sensor
    will be the one to show less camera shake, even without in-camera IS/VR.

    To try to simplify this analogy even further, take a laser pointer and hold
    it 6" from a wall and move it side-to-side only 1º and measure the distance
    the dot covered on the wall. Now do the same 1º experiment at 6' and
    measure again. You will see the distance now covered is much wider. This
    is the same principle of why in-camera stabilization doesn't work at long
    focal lengths.





    Rita
     
    Rita Berkowitz, Jan 28, 2008
  9. No. The distance has to be the same.

    For an image to be sharp, there's an allowable amount of shake, call it "D".

    It's the same for a 100mm lens and a 200mm lens. (It's not about the focal
    length, it's about the sensor.)

    That's the distance the image moves in 1/100 sec for a 100mm lens and 1/200
    sec for a 200mm lens.

    For the 100mm lens, a 2 stop IS function holds the 4*D motion due to a 1/25
    sec to the motion that normally occurs in 1/100 second.

    And for the 200mm lens, a 2 stop IS function holds the 4*D motion due to a
    1/50 sec to the motion that normally occurs in 1/200 second.

    Both the target distance (D) and the rescued distance (4*D) are the same.

    For focal lengths such that the frequence of shake is slow relative to the
    shutter speeds invoved.

    David J. Littleboy
    Tokyo, Japan
     
    David J. Littleboy, Jan 28, 2008
  10. Wouldn't they all be much better if you used Canon.....?
     
    David Springthorpe, Jan 29, 2008
  11. In the case of a simple single convex lens you would be correct,
    because the focal length is the distance from image plane to the
    optical centre of the lens, which in this case is in the middle of the
    glass. In compound camera lenses of short focal length the optical
    center of the lens, the effective fulcrum or pivot of the image
    foraming light beam is still usually within the glass elements,
    although not necessarily in the middle. Telephoto lenses (and
    telephoto zooms) are a special case. Because they would be
    inconveniently long if they were almost as long as their focal
    lengths, they are specially constructed to have remote optical centres
    beyond the front of the lens. In that way they can be more compact
    than their focal length.

    In a focussed camera image the point on the image plane to which a
    point in the view is mapped are connected by a straight line passing
    through the optical centre of the lens. After the camera is wobbled
    slightly the new position of the image point on the image plane still
    lies on a straight line through the optical centre of the lens because
    the optical centre is defined as the point through which all straight
    image forming rays pass.

    If you double the focal length you double the distance of the optical
    centre from the image plane and thus double the shift in position on
    the image plane. It is purely a question of focal length, which is the
    distance from the image plane to the optical centre of the lens, which
    in the case of a telephoto lens is way out in front of the front
    lens. The position of the actual glass of the front lens doesn't
    matter, nor does the position of back lens.

    What matters is the optical centre, in effect the fulcrum of your
    analogy. It is defined to be that point in straight line image forming
    rays. It often differs from the physical centre of glass, and in the
    case of the telephoto it is way out in front of any of the
    glass.

    Where the back lens of a compound lens lies is irrelevant.
     
    Chris Malcolm, Jan 29, 2008
  12. OK. What you say does make sense.




    Rita
     
    Rita Berkowitz, Jan 29, 2008
  13. Okay. You're right.
    Yes, that's the qualifier that makes me believe a "2-stop IS function" (or
    any specific number of stops) doesn't hold all the way down. I think that
    once you get down past 1/8 or maybe 1/4 second the camera shake during
    exposure becomes more complex and the IS is less likely to be effective.
    Getting close to a full second I'd be surprised if it does any good at all.
    But I've never tested this.

    Neil
     
    Neil Harrington, Jan 29, 2008
  14. Why? You're still stuck on the idea that the rear element is some sort of
    fulcrum or hinge, around which everything must rotate. But that's not true.
    Focal length is measured from the second nodal point of the lens (wherever
    that is, and it's not necessarily even inside the lens) to the film or
    sensor plane. If there's a fulcrum, that's where it is, at the second nodal
    point. And for two 135mm lenses, that nodal point is exactly the same
    distance from the focal plane, regardless of any difference in lens design.
    That's really not relevant to the case of the camera being discussed. No one
    is disputing that angular movement has a greater effect at greater
    distances. In the two examples given (135mm telephoto and 135mm press camera
    lens) there *is* no difference in distance. 135mm is 135mm.

    Neil
     
    Neil Harrington, Jan 29, 2008
  15. ["Followup-To:" header set to rec.photo.digital.slr-systems.]

    Nope: even with Canon, one must press the shutter button in the
    right circumstances, at the right moment, pointing the camera in
    the right direction ...

    -Wolfgang
     
    Wolfgang Weisselberg, Jan 30, 2008
  16. Manzoorul  Hassan

    Noons Guest

    Pretty soon. And at 24MP too...
     
    Noons, Jan 31, 2008
  17. Manzoorul  Hassan

    k Guest

    |
    | >
    | > >And there's no reason now with Nikon's
    | > >great FF sensor technology
    | >
    | > Isn't that Sony FF sensor technology?
    |
    | Pretty soon. And at 24MP too...


    Thanks:
    we really needed you to mention this, just in case
    we had forgotten how to read the news by
    ourselves...

    (next moron, please...)
     
    k, Feb 5, 2008
  18. Manzoorul  Hassan

    Noons Guest


    Whassamatter, k?
    Your piss poor online "news service"
    not getting enough hits?
    Fuckwit...

    Oh, BTW: that was not news.
    Once again, you demonstrate your
    inability to read English.
     
    Noons, Feb 6, 2008
    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.