My Sigma 18-35mm's AF stopped working (on a C100 MkII with DAF)

[Lintelfilm]

My Sigma 18-35mm 1.8 AF just completely stopped working (on a C100 MkII).

I was in continuous focus mode and I think it *may* have been me adjusting the manual focus ring that caused it to go. But as I understand it the 18-35mm has full time manual override enabled as default. When I attach it to the Sigma Dock the Full Time MF button is greyed out so I can't change it anyway (unlike the 50-100mm which can have it switched on or off with the dock).

Anyways, the 18-35mm AF is back to normal now but it was gone for a good half hour or more and I have no idea what I did to fix it. I've tried to break it again by manual focusing in continuous AF mode but so far it's just freaked out a bit as you'd expect it to (man vs machine - continuous DPAF vs MF) but returned to normal as soon as I stop turning the focus ring. 

The Sigma 1.8 zooms have always made slightly unpleasant noises in continuous AF mode but I'm worried that the 18-35mm sounds worse/"jumpier" since the fault occurred. But it could just be me being paranoid and it always sounded like that.

Anyone else had anything similar happen with the 18-35mm (or any other lens for that matter!)?

[User]

Hi Lintelfilm. I just check this for you on my combo with no issues. All clear and working well even when I manually roll focus during DPAF.

[Lintelfilm]

2 hours ago, User said:

Hi Lintelfilm. I just check this for you on my combo with no issues. All clear and working well even when I manually roll focus during DPAF.

Thanks man. Mine is fine now too I'm just concerned it'll go kaput again during a job. I hate intermittent faults! 

What kind of noise does your's make - is it quite "stuttery"? If I can make time I'll upload a video of the sound mine makes.

[User]

3 hours ago, Lintelfilm said:

Thanks man. Mine is fine now too I'm just concerned it'll go kaput again during a job. I hate intermittent faults! 

What kind of noise does your's make - is it quite "stuttery"? If I can make time I'll upload a video of the sound mine makes.

No sweat, happy to assist.

Yes I definitely get an audible 'clicking' noise as the lens adjusts itself through it's focal range. I'd say it's somewhat 'stuttery.' I've never used any of my lenses in DPAF mode so I might not be the best person to comment on this. In a quiet room the sound would be picked up by the onboard mics. However, I just compared the sound between the Sigma and a Canon 16-35mm f4 IS and they seemed about the same. Hope this helps.

I've never used an STM lens - which are, as we know, is somehow new technology is supposed to be quite quiet.

[Lintelfilm]

On 27/10/2016 at 7:25 PM, User said:

I've never used an STM lens - which are, as we know, is somehow new technology is supposed to be quite quiet.

I have all the STM zooms and the 50mm 1.8. The prime is pretty noisy. The zooms are very quiet. I think though that smaller apertures are quieter as them dont have to work as much to get focus (because of shallow DOF). 

I love the look of the sigma 1.8 zooms on the c100. I never really use the STMs but they're good to have in a pinch because of IS, focal range, STM, etc

 

[Shield3]

Speaking of the Sigma 18-35, it's the only "designed for APS-C" lens I am keeping in my kit; it does not vignette at all on the 1dx II in 1.4x 4k.  It's a stunner of a lens!