Sony SAL100M28 macro: problems photographing insects

Discussion in 'Digital Cameras' started by Don Tuttle, Jan 15, 2011.

  1. Don Tuttle

    Don Tuttle Guest

    I would like to be able to photograph insects (e.g., bees) up close
    with my Sony A33 and Sony SAL100M28 macro and also get the entire
    insect to be in focus. With this lens, in order to get depth of field
    that will enable me to get the insect body in focus, I have to move
    several inches from the insect. DOF is virtually nonexistent at
    minimum focus distance (.352 meters). At that focal distance, the DOF
    is zero up thru f11. At f16-f32 DOF is only 1 to 2 mm, which is not
    enough DOF to get enough of the insect in focus.

    Do I have an appropriate lens for what I want to do, or would I be
    better off with the SAL50M28?

    (a rookie)
    Don Tuttle, Jan 15, 2011
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  2. Don Tuttle

    Alan Browne Guest

    The 50mm will need you to be even closer to the insect. I don't think
    the DOF will change enough to matter much.

    Insects are challenging - I'm hopeless at it...

    Using the same lens as your 100 f/2.8 (the Minolta version - same thing

    Note this was not at 1:1. The DOF, as you can see does not make the
    entire insect in-focus.

    This guy's pretty good (!) at insects. Still not totally in focus:
    He uses a 65mm lens.
    Alan Browne, Jan 15, 2011
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  3. Don Tuttle

    Ofnuts Guest

    In macrophoto the DOF is about independent from focal length and is in
    practice related to the size ratio between the subject and its image on
    the sensor(*). In other words, with a shorter lens, you'll have to get
    closer but it won't improve your DOF. You can interpret that as having
    your in-focus subject within a parallelepiped with a fixed aspect ratio
    (once you have set aperture): it will become thinner as you reduce the
    height and width when closing in.

    The concept of DOF is however a bit blurry nowadays. It used to be based
    on a circle of confusion equal to 1/1780th of the sensor diagonal, but
    now with pixel peeping the circle of confusion for many people is one
    pixel on the sensor which is, on current cameras, 3 to 4 times smaller.
    Your pictures may look out of focus when pixel-peeping but OK when
    looking them from far enough to see the full frame.

    From what has been said above, you can infer that if you don't try to
    get too close you can get your insect in acceptable focus. My personal
    technique is to keep the insect to at most 1/3 of the frame and shoot it
    centered. This gives more DOF and lets the camera use its most accurate
    AF point. I reframe in post-processing to make a more aesthetically
    pleasing photo (with 14 Mpixels, you can crop a lot).

    (*) a corollary is that since, to produce a picture where the insect
    fills the whole frame, you need a bigger image on a 24x36mm sensor than
    on an APS-C one, and a much bigger image on an APS-C sensor than on a
    compact camera, you have very little DOF on full-frame cameras, slightly
    more on APS-C cameras, and a very deep one on compact cameras.
    Ofnuts, Jan 15, 2011
  4. Don Tuttle

    Alex Monro Guest

    I don't want to get involved in the DSLR / ultrazoom flame wars, but if
    you want more DoF for macro, the smaller sensor of the bridge camera can
    be an advantage. Although the built in macro mode can be limited to
    wide angle, if you use a supplementary close up lens that screws on the
    front like a filter, e.g. Raynox, you can get more visible DoF for the
    same print magnification at a reasonable working distance. If the
    light's good, you can keep low ISO, and noise isn't too much of a problem.

    Another technique is focus stacking - take multiple shots, varying the
    focus slightly, and blend them in PP - you need the insect to keep still,
    though I've heard of people putting them in the freezer for a few
    minutes to chill them out! :)
    Alex Monro, Jan 16, 2011
  5. Don Tuttle

    Bruce Guest

    Indeed, almost the sole reason for shoosing a longer focal length (for
    example 100mm against 50mm) is to obtain a greater working distance.
    There is another reason, though. If you buy carefully you can get a
    macro lens that also doubles as a portrait lens.

    On full frame, that means a focal length between 85 mm and 105mm. On
    APS-C, anything between 55 mm and 70mm will be just fine.

    However, there is one caveat: some macro lenses make very bad portrait
    lenses because they are almost too sharp and have harsh bokeh. The
    most suitable macro lenses for portraiture have their optical roots in
    the 1980s. The Tamron 90mm f/2.8 is among the very best of these.
    Bruce, Jan 16, 2011
  6. Don Tuttle

    Paul Furman Guest

    Interesting lens the way it extends:
    You'll have to stop down to f/32 for more DOF although that will lose
    critical sharpness from diffraction, that's your goal as stated. Adding
    a 1.4x teleconverter with give f/64 and increase your working
    distance... and impact image quality, plus you'll probably need flash to
    get usable shutter speeds. Check out what happens to mtf at f/22:

    Another thing to check is whether the minimum aperture changes at close
    focus. If it still allows an f/2.8 setting, that means the real aperture
    numbers will be larger per this formula: f-number(mag+1).

    32 (1+1) = f/64

    Now, if you want to try focus stacking, then you can use an optimal
    aperture of f/11, and if that calculation needs to be added, you'll want
    to use about f/5.6 to get a final f/11 and it will take probably 50
    frames to capture the maximum detail. It is sometimes possible to take a
    quick succession of hand held focus stacks, although very difficult!
    because you'll want to be stopped down a fair bit and shutter speed will
    be a problem plus most insects will fidget unless you catch them
    sleeping in the morning when it's cold.
    Paul Furman, Jan 17, 2011
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