Are some mirror lenses better than others?

Discussion in 'Digital Cameras' started by Paul Ciszek, Jul 10, 2012.

  1. Paul Ciszek

    Paul Ciszek Guest

    I meant that, while I can buy threaded hardware to attache a Sony/Minolta
    lens to my Olympus OM-D E-M5 camera, I don't expect them to talk to each
    other electronically. Hell, my camera can't seem to make an Zuiko 50-200mm
    lens autofocus properly, and that is made by the same manufacturer and
    belongs to a related standard.
     
    Paul Ciszek, Jul 12, 2012
    #41
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  2. Paul Ciszek

    Alan Browne Guest

    The TC magnifies. You (should) get more overall resolution (detail),
    but not as much as a dedicated, good lens at that focal length.

    Note that you lose speed as well. An f/8 with a 2x TC becomes f/16.
    You'll need a very solid tripod to get sharp shots in even good lighting.

    Everyone I know who bought a 500 reflex ended up using it less and less
    and it eventually kept time in its case, in the closet.

    Alone. In the dark.
     
    Alan Browne, Jul 12, 2012
    #42
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  3. That would have been me too, if I'd have had to focus mine
    manually. Desperately tricky and slow to get good sharp focus
    manually. But I have the Sony 500mm reflex which autofocuses. That
    makes a huge difference to how useful the lens is.

    The remaining very tricky problem once focus has been solved is
    aim. Like a powerful telescope a 500mm lens is difficult to aim,
    especially on a crop sensor DSLR. That made catching moving wildlife
    difficult, and birds in flight verging on the impossible.

    So I added a red dot gunsight to the lens. Amazing improvement! I can
    instantly point the lens at what I want to shoot so easily that I can
    track birds in flight accurately enough for the central spot autofocus
    to lock and shoot -- the central spot focus sensor is the only one
    which can focus this lens. Catching birds in flight or footballers in
    mid kick has become easy and fun.

    It's become so easy to use it's now one of my often-carry-just-in-case
    lenses. I've adapted my bag to have the right shaped pocket to carry
    it with mounted gunsight.
     
    Chris Malcolm, Jul 12, 2012
    #43
  4. Paul Ciszek

    Chemiker Guest

    Makes sense. Wife has a Meade that calculates at 2000MM FF, but
    contrast really sucks. I never use it because of that.

    Alex
     
    Chemiker, Jul 13, 2012
    #44
  5. Paul Ciszek

    Alan Browne Guest

    Interesting adaptation. One of those I spoke about who lost faith in
    the lens had the Minolta AF version as well. I'll mention it to him if
    I run into him (haven't seen him in a few years).

    Do you have a photo of your setup?
     
    Alan Browne, Jul 13, 2012
    #45
  6. Paul Ciszek

    PeterN Guest

    On 7/11/2012 11:15 PM, Paul Ciszek wrote:

    At its ending.
     
    PeterN, Jul 13, 2012
    #46
  7. Paul Ciszek

    PeterN Guest

    Enjoy
     
    PeterN, Jul 13, 2012
    #47
  8. Paul Ciszek

    Guest Guest

    no, because there's always a bigger infinity that extends beyond it.
     
    Guest, Jul 13, 2012
    #48
  9. Paul Ciszek

    Savageduck Guest

    That's just loopy!
     
    Savageduck, Jul 13, 2012
    #49
  10. Paul Ciszek

    Rich Guest

    It should be in focus about 3500ft to infinity. The clock could be
    closer
     
    Rich, Jul 13, 2012
    #50
  11. http://www.flickr.com/photos/chris_malcolm/6988604951/

    That's a photo of the first trial implementation, looked pretty
    scruffy, and wobbled enough that the sight often hd to be
    recalibrated. I tightened it up with more glue and a pair of rubber
    bands to clamp the tube more firmly on the lens barrel. That worked
    well and reliably enough not to require calibration of the sight after
    every removal and replacement on the lens. So I've painted it all
    black to make it look neater until I get around to devising a metal
    version, which I'll probably base on the cheap long metal lens hoods
    you can get for the lens.

    Here's a photo inlcuding that long lens hood on the end.

    http://www.flickr.com/photos/chris_malcolm/6842482858/

    That hood BTW is supposed to reduce flare and improve contrast. Well,
    mirror lenses are inherently low in contrast, and also seem to be
    unusually prone to flare. But adding that hood didn't noticeably
    reduce flare or improve contrast in the few simple tests I did. So
    while flare might be present and the longer hood be a slight
    improvement, perhaps a big improvement if shooting near the sun, it's
    not generally speaking an obvious problem with this latest version of
    the lens. It's clear from careful scrutiny of the existing hood and
    what can be seen of the lens interior that a lot of care has been
    taken to minimise internal reflections, more than in any other lens
    I've seen.

    The existing hood BTW is thought by many to be fixed. It isn't. it's
    just scarily hard to remove unless you know the antideformation filter
    ring removal tricks which makes it very easy. That photo shows the
    existing hood remounted as an extension on the end of the metal
    exension hood, which is threaded at both ends.
     
    Chris Malcolm, Jul 13, 2012
    #51
  12. Out of camera jpegs of my Sony 500mm reflex are noticeably flatter in
    contrast than from a refractive lens. But a simple boost of contrast
    in post processing fixes it. Many editors have a simple "fix contrast"
    button which does it instantly and is usually all that's needed. If
    I'm preparing a shot for an exhibition I'll carefully crop off both
    ends of the tone curve and improve microcontrast with some
    sharpening. The end result looks as good as a good refractive lens
    shot, except of course for the rather fierce bokeh.

    Of course that "as good as" assumes good enough conditions to give
    enough latitude for the editing boosts. In marginal conditions the
    refractor will easily and obviously win.

    If that is you had that big heavy 500mm refractor lens with
    you. There's no 500mm refractor small and light enough to carry around
    in the bag just in case and easily use hand held.
     
    Chris Malcolm, Jul 13, 2012
    #52
  13. Paul Ciszek

    PeterN Guest

    And curves back to the point of beginning.
     
    PeterN, Jul 13, 2012
    #53
  14. Paul Ciszek

    PeterN Guest

    Like many comments on Usenet. ;-)
     
    PeterN, Jul 13, 2012
    #54
  15. Paul Ciszek

    PeterN Guest

    PeterN, Jul 13, 2012
    #55
  16. They also don't have a Bayer filter.
    And the airy disk there is usually a bit larger than a pixel, IIRC.

    -Wolfgang
     
    Wolfgang Weisselberg, Jul 13, 2012
    #56
  17. Paul Ciszek

    Paul J Gans Guest

    Those are amazing shots, simply amazing. And the red-dot sight
    is a great idea! I'm surprised that the cardboard "clamp" provides
    enough rigidity.
     
    Paul J Gans, Jul 13, 2012
    #57
  18. At long last I got round to measuring the distance between my vantage
    point and the clocktower using google maps. It's not two miles away,
    almost exactly a mile in fact. So you're right -- it is closer!

    I've also photographed that clock tower from the roof of my house,
    which is about 3,700 feet away. From my roof there is a nearby hill a
    few miles further away which is out of focus if the clock is in focus,
    and vice versa, however. So I'm clearly being a bit fussier about
    sharp focus than the assumptions behind your DoF calculation.

    The image BTW is 14MP taken with a 500mm lens on a 1.5 crop sensor.
     
    Chris Malcolm, Aug 15, 2012
    #58
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