If it's like the Sigma 30/1.4 there's no clutch on the lens. When the
camera is in auto-focus mode the motor stays engaged. Switching the
camera to manual focus retracts the motor drive pin on the camera.
The manual focus ring follows auto-focus like the manual focus ring on
the Pentax FA-J 18-35 zoom. It can be disconcerting if you're used to
holding on to the manual focus ring while auto-focusing, because the
focus ring will jerk.
From: Boris Liberman
Larry, isn't there a some kind of clutch that you have to engage or
disengage prior to going manual focus?
On Thu, Dec 10, 2009 at 10:26 AM, Larry Colen <[email protected]> wrote:
Does anyone else have the 20/1.8?
Optically it seems like a sweet piece of glass. Unfortunately
while I needed it last weekend, it didn't show up until Monday
and I haven't had a lot of time to play with it.
The first thing that I noticed was that in manual focus, focusing
?it felt like it was turning a motor.
It also turns out that if the lens is in manual focus, and the
camera is in auto focus, autofocus still works, it's just that
the focus ring won't turn when the camera focuses.
Looking on the mount, when I manually focus, the drive gear for
the autofocus will turn.
The big problem is that this makes the lens unpleasant to
manually focus, though it works fine, it feels bad. Is this the
way it's supposed to work? Or do I have a bad copy of the lens?
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