 BetterPhoto Member |
Focus Problem In a Zoom Lense dear Sir I have a AF NIKKOR 28-200mm Zoom Lense. If I focus an object at 28 mm and then just Zoom in at 200 the Focus does not remain the same while the Object and The Camera Positions are Fixed. Why Should the Focus change ?? Thanx
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Jon Close |
There are 2 different zoom lens designs - Parfocal retain focus when zoomed while Varifocal will change focus. Parfocal are generally more difficult to design, especially for autofocus lenses (where the mechanism and number of focus elements is kept simple for faster af), so many (if not most) consumer af zooms are varifocal. Often the instructions for the lens and/or the camera will advise that the lens must be refocused after changing the zoom.
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