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10-13-2017, 01:31 PM   #1
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Sigma 17-70mm f2.8-4 C stiff AF

Hi,
Has anyone experienced a stiff focussing ring with the above lens? Let me describe the problem:
I got the Sigma 17-70 C new a year ago and I've been using it regularily on a K3. About a month ago I noticed that (in AF mode) the motor whirrs and beeps but the lens does not attain focus. When switching to MF I noticed the focusing ring turns quite stiffly. After a few manual turns back and forth it turns more easily, but I don't remember exact how loose/smoothly it ougth to turn. Problem appears to get worse and I get the impression its worse when battery power is on low side.
Any thougths or similar experiences with this (or other) Sigma? Is the lens faulty? Haven't checked if it still under warranty. Should I?

10-13-2017, 02:05 PM   #2
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QuoteOriginally posted by Marcel K Quote
Is the lens faulty? Haven't checked if it still under warranty. Should I?
Sounds like it might be on the verge of failing. I would get it inspected.

Adam
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10-13-2017, 03:06 PM   #3
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QuoteOriginally posted by Marcel K Quote
Hi,
Has anyone experienced a stiff focussing ring with the above lens? Let me describe the problem:
I got the Sigma 17-70 C new a year ago and I've been using it regularily on a K3. About a month ago I noticed that (in AF mode) the motor whirrs and beeps but the lens does not attain focus. When switching to MF I noticed the focusing ring turns quite stiffly. After a few manual turns back and forth it turns more easily, but I don't remember exact how loose/smoothly it ougth to turn. Problem appears to get worse and I get the impression its worse when battery power is on low side.
Any thougths or similar experiences with this (or other) Sigma? Is the lens faulty? Haven't checked if it still under warranty. Should I?
With the MF/AF switch on the lens in the "MF" position, the focus ring should move quite easily with almost no resistance. Moving the MF/AF switch to "MF" physically disengages the ring from the AF drive.

With the MF/AF switch on the lens in the "AF" position, the focus ring should NEVER be moved manually, regardless of whether the camera is powered on or the position of the body MF/AF switch. Doing so risks serious damage to the lens. The in-depth review on this site wrongly asserts in the specification table that this lens has "quick-shift" manual focus adjustment when it does not.

If your lens is still under warranty, it may be time to send it in.


Steve
10-13-2017, 03:53 PM   #4
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Hi Adam, Steve,
Thanks for your quick reply. Yes I only used the af/mf switch on the lens to get mf and are aware quick-shift is a no go 🤓. Although af seems to work (for now) i may get the lens checked as you suggested. Cheers

10-13-2017, 06:09 PM   #5
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Many 3rd party lenses having a MF/AF switch will work best if the camera body MF/AF switch is also engaged accordingly.
10-14-2017, 02:30 AM   #6
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@Mike, do you mean: to operate MF on a 3rd party lens w AF/MF switch I should set BOTH lens AND camera switches to MF? (unless when using catch-in focus). That's new to me...
Please elaborate
10-15-2017, 03:36 AM   #7
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QuoteOriginally posted by Marcel K Quote
That's new to me...
New to me as well...examples?


Steve
10-16-2017, 05:27 PM   #8
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I would think using a lens like the Sigma 17-70C, which has no screw drive capability, it wouldn't matter at all what position the camera switch was in when using the lens in MF.

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