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Thread: Apature

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  1. #17
    Join Date
    Jul 2004
    Quote Originally Posted by Razr View Post
    If you read your own definition, it is not correct: Av mode means the aperture is locked on a given f/stop while the shutter is used to balance the exposure, as per Wikipedia (or any other resource)


    Got it?
    Yes, I got it now. Let's look at Wikipedia
    The maximum aperture for a zoom lens may be same for all focal lengths, but it is more common that the maximum aperture is greater at the wide-angle end than at the telephoto end of the zoom range. For example, a 100 mm to 400 mm lens may have a maximum aperture of 4.0 at the 100 mm end but only 5.6 at the 400 mm end of the zoom range.
    I certainly got that a zoom lens may have a different max aperture at the short and long ends.

    Let's look at another resource, say the manufacturer of your 4/3rds cameras of choice(Olympus):
    Olympus/Zuiko makes some variable max-aperture zoom lenses for their 4/3rds cameras. I especially like how they have DOF values on their website for their lenses.




    What I can't understand is why there is no DOF info on these lenses at the middle range or long end for say f/2.8 and no DOF info on these lenses at the long end for say f/3.2. Could it possibly be because Olympus/Zuiko does not know how to "lock" the aperture at f/2.8 in Av mode for the entire zoom range, or because zooming these lenses causes the max aperture to change from f/2.8 to f/3.5 as it says in their literature/website. Hmmmmmmmmm?

    edit: I hope that this is not just a limitation of the 4/3rds format.

    Last edited by Ray Schnoor; 10-25-2007 at 07:44 AM.

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