Problems Focusing on Small Blue Things

Discussion in 'Digital Photography' started by Randle Hurley, Oct 19, 2003.

  1. I'm interested in photographing wild flowers in their natural habitat. I
    use a Kodak DX3900 camera in macro mode with combinations of Kodak's +7
    and +10 macro lenses. Some of the flowers are very small but I have
    managed to get well focussed shots of most, except the pale blue ones.
    I've even tried focussing on something red, held beside the target and
    then removing it before pushing the button the rest of the way down.

    Is blue difficult for auto focus to deal with or have I just been
    unlucky? I'm 1000 shots into the project now so it feels like a real
    problem to me. I have used the centre weighted focus option instead of
    centre spot because shots with a single flower dead centre get a bit
    dull after a while.

    A related question; the manual says to switch off flash while in macro
    mode but doesn't say why. What happens when you switch to macro mode? Is
    it just that the flash distribution is poor when the lens is close to
    the subject?

    Thanks in advance for any replies.
     
    Randle Hurley, Oct 19, 2003
    #1
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  2. Randle Hurley

    CSM1 Guest

    For critical focus, you must use a tripod.

    Have you tried spot meter, half press the release button then move to frame
    the shot, press button rest to the way down. If you can not get focus, maybe
    you are out of the range of the lens.

    From Kodak web site for DX3900:
    focus distance standard: 0.50 m - infinity, (1.6 ft. - infinity);
    macro-wide: 0.07 m - 0.7 m (0.2 - 2.3 ft.); macro-tele: 0.25 m - 0.7 m
    (0.8 - 2.3 ft.)

    macro-wide 0.07m=2.76 inches or about 2 3/4 inches
    macro-tele=0.25m=9.8425 inches or about 9 13/16 inches, call it 10 inches.

    Focus distance is measured form the plane of the image (the ccd sensor), to
    the subject.
    Plane of the image is not the front of the lens.

    The reason to turn off the flash in Macro is you get the shadow of the lens
    in the picture.
    The lens is so close to your subject that the on camera flash makes a
    shadow.
     
    CSM1, Oct 19, 2003
    #2
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