Re: macro photography - partial success and mystery

Discussion in 'Digital Photography' started by Bill T., Feb 18, 2010.

  1. Bill T.

    Bill T. Guest

    On Thu, 18 Feb 2010 10:52:21 +0000, bugbear
    <bugbear@trim_papermule.co.uk_trim> wrote:

    >
    >Can anyone explain the optics of what I'm doing, and how to optimise
    >the system for best results - in particular subject-lens distance,
    >lens-camera distance, and camera focal length?


    Without knowing the exact components involved in your whole optical train,
    that would be impossible. If the "magnifier" that you are using was
    salvaged from an older lens, chances are good that it's an achromat. And
    might very well be anything that's better than what you can buy today as a
    close-up adapter.

    Do you see a very thin line along the rim of the lens where it appears that
    two glass elements are cemented together? Then it's an achromat. The best
    of close-up lenses available. And, while it may not be optimized to perform
    as best as can be expected if taking the whole optical-train into account,
    they can still produce excellent results with most lens designs when used
    as an add-on +diopter close-up lens. I, myself, use several of these
    salvaged lenses from old housings, from +8 to +12 diopters in strength.
    None of them performing poorly on any camera they are mated to. Because
    what is offered on the market today rarely compares to older achromats
    designed for earlier SLR lens designs.

    I think you are over-analyzing this to no real useful purpose. I didn't
    even waste my time looking at your posted images, because there are some
    basic principles that will always take precedence. The most significant
    being that if the subject matter is good it will always override that
    intangible thing everyone calls "image quality". If the clarity is good
    enough to please you, then it should be good enough to please anyone else
    .... again, depending on if the subject matter and composition overriding
    any deeper inspection. If people are looking at your pixels then you've
    obviously done something very wrong with basic photography principles to
    begin with.

    Bottom line, in a pinch, I've even borrowed someone's reading glasses to
    hold in front of the camera's own lens to obtain an important macro shot.
    If the results were acceptable and the subject matter would always keep the
    viewer's eye from inspecting pixels. That's all that really matters, if the
    subject was important enough so that people were in awe over the subject
    rather than the pixels.

    And wherever did you get the idea that a reversed SLR lens (in total) can't
    be used as a very effective close-up lens when attached that way to the
    front of a P&S camera? Someone has been delivering to you a full acre of
    bullshit and you bought it with no questions asked.

    Are you a photographer? Or just another useless pixel-peeping gear-head.
    Bill T., Feb 18, 2010
    #1
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  2. Bill T.

    Richard Guest

    "Bill T." <> wrote in message
    news:...
    > On Thu, 18 Feb 2010 10:52:21 +0000, bugbear
    > <bugbear@trim_papermule.co.uk_trim> wrote:
    >
    >>
    >>Can anyone explain the optics of what I'm doing, and how to optimise
    >>the system for best results - in particular subject-lens distance,
    >>lens-camera distance, and camera focal length?

    >
    > Without knowing the exact components involved in your whole optical train,
    > that would be impossible. If the "magnifier" that you are using was
    > salvaged from an older lens, chances are good that it's an achromat. And
    > might very well be anything that's better than what you can buy today as a
    > close-up adapter.
    >
    > Do you see a very thin line along the rim of the lens where it appears
    > that
    > two glass elements are cemented together? Then it's an achromat. The best
    > of close-up lenses available. And, while it may not be optimized to
    > perform
    > as best as can be expected if taking the whole optical-train into account,
    > they can still produce excellent results with most lens designs when used
    > as an add-on +diopter close-up lens. I, myself, use several of these
    > salvaged lenses from old housings, from +8 to +12 diopters in strength.
    > None of them performing poorly on any camera they are mated to. Because
    > what is offered on the market today rarely compares to older achromats
    > designed for earlier SLR lens designs.
    >
    > I think you are over-analyzing this to no real useful purpose. I didn't
    > even waste my time looking at your posted images, because there are some
    > basic principles that will always take precedence. The most significant
    > being that if the subject matter is good it will always override that
    > intangible thing everyone calls "image quality". If the clarity is good
    > enough to please you, then it should be good enough to please anyone else
    > ... again, depending on if the subject matter and composition overriding
    > any deeper inspection. If people are looking at your pixels then you've
    > obviously done something very wrong with basic photography principles to
    > begin with.
    >
    > Bottom line, in a pinch, I've even borrowed someone's reading glasses to
    > hold in front of the camera's own lens to obtain an important macro shot.
    > If the results were acceptable and the subject matter would always keep
    > the
    > viewer's eye from inspecting pixels. That's all that really matters, if
    > the
    > subject was important enough so that people were in awe over the subject
    > rather than the pixels.
    >
    > And wherever did you get the idea that a reversed SLR lens (in total)
    > can't
    > be used as a very effective close-up lens when attached that way to the
    > front of a P&S camera? Someone has been delivering to you a full acre of
    > bullshit and you bought it with no questions asked.
    >
    > Are you a photographer? Or just another useless pixel-peeping gear-head.


    No need to ask whether you're a pompous idiot.
    Richard, Feb 18, 2010
    #2
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  3. Bill T.

    Bill T. Guest

    On Thu, 18 Feb 2010 12:20:24 +0000, bugbear
    <bugbear@trim_papermule.co.uk_trim> wrote:

    >Bill T. wrote:
    >
    > > If the clarity is good
    >> enough to please you, then it should be good enough to please anyone else

    >
    >But it isn't!
    >


    Have you tried something as simple as reversing the lens? In the case of
    achromats (as well as simple lenses with different curvatures on each face)
    this can make a huge difference. You might have the wrong face toward
    subject and camera. If that doesn't help then you might want to search for
    a different achromat to play with. If you can't get a clear image with the
    one you are attempting to use then the curvatures of the glass are just too
    different to work well with your camera's optics as a close-up adapter
    lens.

    Without you having access to an optics course, there are some basic
    principles for simple optics designs that tend to apply across the board.
    Look to any chart of telescope eyepiece designs to see how 1 or 2 achromats
    are implemented for optimal CA performance and field flatness. A quick
    Google search found these overview charts of many of the more popular
    designs. It sounds like your achromat's curvatures may not work well as a
    single element close-up lens when mated to the curvature of glass at your
    camera's entrance pupil. You might try implementing it as a Kellner, RKE,
    König, or Plössl configuration.

    http://www.jb.man.ac.uk/astronomy/nightsky/eyepiece.jpg

    Another

    http://www.telescope-optics.net/images/eps2.PNG

    Failing that, and if you have access to some non-achromat planar-convex
    lenses out of your salvaging project you might try the simpler Ramsden
    design for a close-up lens. At lower f/ratios it's surprisingly simple and
    effective. Compare its point-spread patterns in the second chart above to
    the others. Most inspection and jeweler's loupes are of this design. The
    more expensive larger f/ratio ones being in a Kellner configuration which
    implements an achromat. Some going as far as using the Abbe design winch
    implements a triplet for even better performance.
    Bill T., Feb 18, 2010
    #3
  4. Bill T.

    Bill T. Guest

    On Fri, 19 Feb 2010 09:43:57 +0000, bugbear
    <bugbear@trim_papermule.co.uk_trim> wrote:

    >
    >You can actually get 4 element loupes.
    >For reasons unrelated to this thread, I've got one.
    >
    >http://www.quicktest.co.uk/acatalog/Jewellers_Loupes__under__20_00.html


    It's probably a Plössl configuration. 2 cemented achromats. Optic
    assemblies are counted by the individual lens elements in the system. So an
    optic design of that type would be defined/labeled as: 4 elements in 2
    groups. It could even have an Abbe configuration. 1 achromat triplet and 1
    single. This would also be defined as 4 elements in 2 groups. Though the
    price listed makes that less likely. Achromats of nearly any size are
    already more expensive to produce. Triplets even more so. A good quality
    achromat of only 60mm (~2.4 inches) in dia. for spotting scopes and
    finder-scopes, just the lens alone without any housing, can easily cost
    upward of $50

    I was lax in calling an achromat a single lens "element" in one of my
    previous comments. It's considered a "group". However using that term in
    the previous context would have sounded confusing to someone less aware of
    optics design nomenclature. I.e. "It sounds like your achromat's curvatures
    may not work well as a single _group_ close-up lens when ..."

    A cemented triplet is also called a "group". 2 unconnected elements, as in
    an air-spaced achromat (found in very expensive refractor telescopes)
    spaced apart by less than 1mm to a few mm; or a closely spaced assembly
    that remains fixed in relation to each other, comprised of several elements
    where they all depend on each other to provide a required CA or field
    correction rather than actual image focusing; can also be called a "group".
    Though the latter is less commonly called an actual "group". Some do, some
    don't. It's a gray area in optics terminology.
    Bill T., Feb 19, 2010
    #4
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