From: Larry Colen
On Dec 15, 2009, at 3:59 PM, Mark Roberts wrote:
> On 12/15/09 4:29 PM, Carlos R wrote:
>>
>> you must be sure you
>> disengage AF by using both the camera AF/MF switch and also by
>> pushing
>> the focusing ring on the lens towards the camera body, as,
>> unfortunately, these Sigma lenses can't deactivate the AF motor in
>> the
>> camera body only by using the lens clutch, like genuine Pentax FA*
>> lenses do (FA* 24 mm. 2.0, FA* 300 mm. 4.5, FA* 80-200 mm. 2.8 and
>> some
>> others).
>
> I'll second that. Both the Sigma EX lenses I've owned worked this
> way: You need to switch off AF on the camera body and pull the lens
> focus ring toward you. Works very well then. Not as convenient as
> the Pentax FA* lenses, but then again, they're about half the price
> of equivalent Pentax FA* glass :)
I've got no problems with the functionality. It seemed odd,
especially since the AF/M ring on my bigma disengages the drive gear.
It's just got a horribly lumpy feel in manual focus. They said it'll
take 3-4 weeks for them to repair it, so I'll send it in after the
holidays. I've got too much need of it right now.
I have 4 Sigma lenses.
The "Bigma" and the 300/2.8 both have the focus ring that disengages the
drive gear when you shift to MF on the lens. You don't have to turn AF
off on the camera.
The 10-20 & the 30/1.4 don't have AF/MF shift on the lens, so you have
to turn AF off on the camera to use manual focus.
None of my lenses have any kind of "lumpy feel" when using manual focus,
so I think you do have a bad example of the lens.
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