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  1. #11
    Ole
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    All the various chromatic corrections are good only in the visible range. APO or not makes no difference.

    But as I said above, for the near-IR we're dealing with unless using Kodak HIE and some really esoteric filters, the "IR" is close enough to red light that we can ignore all corrections.

    One of my pet peeves is my Russian fisheye lens. Due to the construction, you can only use the filters enclosed with the lens: Clear, yellow, Green, Red.
    It's got an IR mark, so far off that if it were correct for IR, an unfiltered shot would look like it were shot through a stained-glass window. Note that there is no IR filter enclosed...
    -- Ole Tjugen, Luddite Elitist
    Norway

  2. #12

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    I heard another explanation from an optical product specialist in Solms (Leica). Their APO lenses are corrected over 900nm so do not need any focus correction.

    The normal focus correction (red dot) on lenses is valid around 800nm. Due to the fact that most photographers are using wide angle lenses for IR, the problem is not so big because in most cases it's indeed in the DOF.

    Best regards,

    Robert

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