the SDM motor is very thin, and fits outside of the lens elements,
attached to the focusing helicoil. It's the same kind of motor (only
much more precise) that turns the CD in a Walkman or a minidisc player.
This thick --> =======================_^_^_^_^ <-- sensors to
read position.
A 40mm pancake could be made to work with one, especially given the
size of the optical elements.
On May 19, 2009, at 14:13 , John Francis wrote:
On Tue, May 19, 2009 at 02:31:11PM -0400, Mark Roberts wrote:
John Francis wrote:
If Pentax do move to a new range (with a smaller register distance),
I wouldn't be surprised to see auto focus for K-mount lenses only
working with SDM.
That'll never happen as long as the pancake Limited lenses are big
money-makers for Pentax: They're too small for motors to fit in the
lens.
If small size is the goal, then there's absolutely no point in using
a K-mount lens on a body with a shorter register - you have to add an
adapter to provide space between the mount and the lens, which rather
defeats the point of a pancake lens.
Joseph McAllister
[email protected]
http://gallery.me.com/jomac
http://web.me.com/jomac/show.me/Blog/Blog.html
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