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07-15-2013, 11:07 AM   #1
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AF lenses which focus with single movement

I now have two Sigma lenses and both of them hunt while focusing (although they snap quite quickly).

What are the lenses you tried which snap the focus with a single movement? Which bodies did you use?

Do HSM (SDM, USD and etc.) lenses hunt while focusing?

07-15-2013, 11:18 AM   #2
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Hm, I think there was a thread on this recently?
https://www.pentaxforums.com/forums/pentax-k-01/229427-auto-focus-two-step.html
If thats what you are talking about, its a camera thing, but some lenses have AF so fast that its not noticeable.
My fastest AF lens is probably the DA 40mm XS. But I dont really have a lot of AF lenses to begin with.
The lenses with focus motor probably hunt just as much, but they should be more silent and faster to begin with, because the motor is designed with just right power and speed for that lens design.
What probably affects AF more is the lens max. aperture and light conditions (EV of the scene)
In live view the AF type is different, its CD AF instead of PD AF. That AF hunts a little more.
07-15-2013, 11:27 AM   #3
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I think all lenses do that on a Pentax camera. Canon and Nikon seems to use a shorter intervalls between feedback to the camera those turn back quicker to the optimum focus spot.
07-16-2013, 09:01 AM   #4
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QuoteOriginally posted by Na Horuk Quote
Hm, I think there was a thread on this recently?
That one is about K-01, I am talking about phase detect AF.

My Sigma lenses make one huge move (which almost nails the focus) and 3 or 4 very tiny moves. They do not slide back and forth by a huge margin if you are talking about it.

QuoteOriginally posted by VisualDarkness Quote
I think all lenses do that on a Pentax camera.
You are talking about phase detect, right?

07-16-2013, 10:52 AM   #5
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Oh, it could be just your camera settings. AF.C is "continuous". Switch it to AF.S.
07-16-2013, 11:12 AM   #6
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No, it is not.
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