What you're describing is a true zoom lens. Much more common before
AF took over the market. Zoom to the longest focal length,
effectively magnifying what the finder shows, focus, then zoom to the
focal length needed for the pic. One of the reasons I preferred
two-touch zooms; one-touch might drift a bit on the way back.
Vari-focal designs were available in the MF days, but not very common
because they had to be refocused every time focal length was changed.
Some people claimed V-F were better optically and allowed smaller form
factors. Kiron offered a few and Vivitar marketed some.
Most AF lenses are V-F and therefore require refocusing every time
focal length is adjusted. This is accepted because the design
dominates the market and AF makes it easy to make the adjustment even
if the margin of error is greater.
ScottGee1
On 6/19/06, Wayne S <om4t@xxxxxxxx> wrote:
> At 09:17 AM 6/19/2006, Chuck wrote:
SNIP!
> Seems modern lenses, with auto-focus,
> vario-focus zoom effects, etc. all focus past infinity.
> There once was a time I could zoom in, focus, and zoom out.
> WayneS
>
>
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