Telephoto Reach and Digital Cameras - lens comparison

Discussion in 'Digital Photography' started by David J Taylor, Dec 6, 2010.

  1. David J Taylor, Dec 6, 2010
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  2. David J Taylor

    tony cooper Guest

    Yes, anyone intent on taking amateur photographs of the moon from
    their backyard should pay heed to this study. All six of them.
    tony cooper, Dec 6, 2010
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  3. David J Taylor

    Rich Guest

    Side issue;
    Anyone trying to take good moon shots by using a telephoto lens
    instead of a telescope is making a mistake.
    A telescope worth $500 can take far superior images of the moon than a
    $5000 telephoto lens for two reasons: Focal length and aperture.
    Rich, Dec 7, 2010
  4. David J Taylor

    otter Guest

    otter, Dec 7, 2010
  5. Just more of Clark's garbage in, garbage out results. No wonder he was
    fired from so many jobs. His glaringly biased attempts to try to justify
    why he has spent all that money, like every other test he's ever done.

    You'll note that he should have used ISO100 and larger apertures on the
    superzoom, where the images would then have been nearly identical, because
    the superzoom lens improves on resolution at larger apertures, unlike on
    DSLR glass where the figure isn't good enough to hold to
    diffraction-limited resolutions at larger apertures. Instead he made sure
    to use the superzoom on settings where noise and diffraction limitations
    start to set in just to try to make his expensive gear look better to him.

    If you look at both images at pixel level you'll note too that he took a
    higher-resolution image from the DSLR then applied much higher JPG
    compression to the superzoom image.

    He just loves fudging his own tests to get the results he wants, always
    leaving out these important bits of details in his biased explanations. And
    all you fools fall for it, every time, guaranteed.
    Superzooms Still Win, Dec 8, 2010
  6. Hi, Roger, nice to see you back. We don't allow mission posters, haters
    or those spewing 6th grade obscenities to deter us.

    Many have found that simply ignoring this pest is the best we can do.
    I've even prayed for his tormented soul—didn't work!

    You don't need to defend anything, and thanks for your contributions
    over the years.
    John McWilliams, Dec 14, 2010
  7. Hi, Roger, nice to see you back. We don't allow mission posters, haters
    Yes, welcome back. Most of us have simply kill-filed the pest, and I hope
    it's obvious to any newcomers that something which needs to resort to such
    foul language in that manner has little of value to contribute.

    What is perhaps confusing is the effect of diffraction in object space and
    sensor space. As I understand it, in object space - what the camera
    sees - the effect of diffraction can best be visualised in angular terms,
    so that a larger diameter lens has a smaller diffraction "cone" (if you
    like), and hence can resolve more detail on a given surface. In sensor
    space - where the image is produced - the effect of diffraction can be
    visualised making each image spot a finite diameter for a particular
    f/number. When the pixel size is larger than the diffraction spot, the
    pixel size tends to be the limiting factor in resolution, and this can
    happen in large-pixel DSLRs with the best lenses. Where the pixel size is
    smaller than the diffraction spot, the effect of diffraction would be the
    dominant factor in determining resolution.

    So while the small-sensor camera /may/ be closer to diffraction-limited,
    given good enough optics (which is questionable at the price), that
    diffraction limit is a much lower resolution in object space, due to the
    smaller actual diameter of the optics. The ratio of the sensor sizes
    might be 30/6.5 (for an APS-C camera to a "1/2.7-inch" sensor camera) - so
    about 4.5 times, and hence the scale of the optics, and that ratio might
    set the upper limit for the resolution ratio if both cameras had
    diffraction-limited systems working at the same f/number.

    Your comparison shows the benefit of the larger diameter optics....

    David J Taylor, Dec 14, 2010
  8. in message []
    Yes, I can see that about fine detail, I'm still slightly surprised about
    the apparent "flare" in the FZ35 image. I hope to have access to a 1300mm
    f/12.7 telescope soon and may try attaching the Nikon D5000 camera to
    that. 5.5um pixels if I worked it out correctly, so the camera won't be
    the limit but the f/12.7 optics.

    Thanks for your other comments.

    David J Taylor, Dec 15, 2010
  9. Comparing recent cameras and glass that you've thrown away many $1000's on
    to a three year old P&S's images. And this desperate to try to beat a 3
    year old P&S camera for THREE YEARS NOW! And still you fail unless you can
    stack the deck in your favor with misinformation and misleading results.
    How very sad and insecure your life must be.

    Superzooms Still Win, Dec 15, 2010
  10. David J Taylor

    Eric Stevens Guest

    Eric Stevens, Dec 16, 2010
  11. []
    That's a fair comment, Bob. One uses the tools most appropriate to the
    task in hand, and I know that I won't carry such big lenses as Roger uses,
    and I accept the performance will be somewhat worse. I do now use a DSLR
    as it has many advantages for me over the cameras I used before, but I
    still have a pocket camera for those occasions which require it. What
    Roger's page clearly shows is that very small sensors and lenses cannot
    overcome the limitations of physics.

    David J Taylor, Dec 16, 2010
  12. David J Taylor

    peter Guest

    I noticed on your site that you take images with stacked teleconverters.
    It is my understanding that in addition to loss of light a teleconverter
    also exaggerates any flaws in the prime lens. I could not see any such
    exaggeration of aberrations.

    Also, I would think that stacking would work for your astro shots, when
    mounted on a proper tracking mount, but would not be very practical for
    wildlife photography.
    peter, Dec 16, 2010
  13. David J Taylor

    peter Guest

    Absolutely, a gimbal mount works well.
    I was actually referring to stacked teleconverters not being practical
    due to the loss of light. In my own experience the only combination I
    have liked is the Nikkor 1.7 attached to my 70-200. I have tried the
    Kenko 1.4 and the Nikkor 2x on the 80-400, but have not been even close
    to happy with the results.
    peter, Dec 17, 2010
  14. David J Taylor

    Martin Brown Guest

    And more to the point you can hang one on a real telescope at prime
    focus. The only worry is getting dust on the sensor and that some DSLRs
    burn through batteries when used in B mode for long exposures.
    If anything the aberrations are less with a teleconverter as the longer
    effective focal length means the rays going through the lens to the film
    plane are closer to the lens axis and at a shallower angle where all the
    optics approximations hold more accurately. It is the edge of field
    corners where a prime lens has its worst aberrations.

    However, you do need a prime lens that is tack sharp since when you
    multiply the lens focal length by 2x there needs to be something useful
    to go into the additional pixels. Otherwise you could just take the full
    frame picture and interpolate the missing pixels in software.
    When using teleconverters with a telescope which is already a long focal
    length and by comparison with a normal lens many have long back focus
    you can alter the magnification a fair bit by adding extension tubes
    between the teleconverter/compressor and the camera. This does slightly
    affect aberrations but is usually OK.

    Martin Brown
    Martin Brown, Dec 17, 2010
  15. David J Taylor

    me Guest

    Only because Canon doesn't make anything in the class of the Nokon
    200-400mm f/4 VR Ior II.

    me, Dec 17, 2010
  16. David J Taylor

    peter Guest

    Which may be why I have the issue. Have you tried stacking with a 500
    peter, Dec 18, 2010
  17. BFD, even a stopped-clock is right twice a day. Quite frankly I'm suspect
    of whoever judged that improperly exposed and poorly composed zoo snapshot.
    I've posted ones better than that as throw-aways here just for examples to
    prove all these trolls wrong on issues unrelated to marketable photography.

    I stopped entering international competitions when I found out how easy
    they were to win. There's no challenge in winning awards. One time I
    entered a purposely crappy photo just as a joke, to show all my
    photographer friends just what kind of crap-photography will win an award.
    They bet me it would never win. I said, "Wait and watch. They'll actually
    vote on this crap." It won. It was a good laugh. This says so much more
    about the viewer and voter than it does any photographer. One need only see
    the praises handed out on Flickr to comprehend the folly of it all.
    Superzooms Still Win, Dec 18, 2010
  18. David J Taylor

    tony cooper Guest

    You've never posted a link to one of your images that would be
    accepted by one of those neighborhood free papers, let alone a real
    publication. Unless, of course, there's a magazine called "The Rare
    Moth Review" that prints fuzzy, poorly-composed, images that could be
    of a moth or could be of a moldy head of broccoli.
    tony cooper, Dec 18, 2010
  19. David J Taylor

    John Turco Guest

    <heavily edited for brevity>

    Welcome back, Roger! Please, stick around and contribute
    on a regular basis...don't allow Usenet to whither away,
    John Turco, Jan 12, 2011
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