> And that's only the labeled f/stop. The actual f/stop is only valid at
> infinity. The effective f/stop get numerically larger as the extension
> increases.
Doesn't that depend on methodology of focusing? For example, most
modern lens designs use internal-focusing which decrease focal-length
as you focus closer, whereas older designs operate by extending the
entire lens mass forward which keeps the focal length the same.
--
Ken Norton
ken@xxxxxxxxxxx
http://www.zone-10.com
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