At 05:43 PM 6/25/01 +0200, you wrote:
>
>And a different, general question:
>
>Why do newer lenses offer inferior aperture values? I thought that new
>materials and forumlas could permit for brighter lenses?
They do. Zoom lenses have been around for a while, but the constant
aperture F2.8 such as 80-200mm F2.8 are more recent. But these lenses are
terribly expensive. The typical SLR buyer would rather pay $150 for a
slower, variable aperture zoom than $1000 for the fast, F2.8 aperture zoom.
Also, with newer SLRs, constant aperture zooms are less important. For
something like manual flash, thyristor flash, or using an external light
meter, knowing the exact aperture value is important (something not
possible at all focal lengths on a variable aperture zoom). With better
built in light meters and TTL flash, a constant aperture zoom is not as
important to most people.
>
>In fact I was told that the maximum aperture does not depend on the
>quality or groups of the lenses, but only on geometry (front lense,
>length)?
True.
>
>I do not get this point, since the 35/105 is labeled 'f/3.5' for the full
>range.
There are a few tricks involved in doing this, that's why these lenses are
more expensive than variable aperture lenses. One of the tricks is using
the aperture blades. At the shorter ends the 35-105mm F3.5 lens is
actually stopped down just a little bit - otherwise it would be something
like a 35-105mm F3.0-F3.5 lens.
Todd
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