Focus Question Regarding Sigma Lens On A7riii

Started 2 months ago | Discussions
Mecca66 Regular Member • Posts: 183
Focus Question Regarding Sigma Lens On A7riii

I recently bought a Sigma 35mm 1.2 lens which I use on an A7riii. The lens takes great pictures and the focusing is spot on. My question is, when I have the camera in AF-S, when I touch the shutter to achieve focus, there is a light thump or thud or jump within the lens just before it achieves focus. There is no audible noise, just the thump which you can feel. Focusing is not adversely affected as focus is fast and accurate. This does not occur at all in AF-C which is what I normally use. Has anyone else experienced this with this lens, or any other Sigma or Sony lens for that matter? Just wondering if this is within the norm.

Impulses Veteran Member • Posts: 8,451
Re: Focus Question Regarding Sigma Lens On A7riii
1

AF-S still performs a CDAF check (focusing it back and forth to check contrast), whereas AF-S just moves it directly to where the OSPDAF thinks it should go... Might be what you're feeling? Does it feel similar to when you AF-C on something that's moving?

 Impulses's gear list:Impulses's gear list
Panasonic GX850 Sony a7R IV Olympus M.Zuiko Digital ED 75mm F1.8 Panasonic Lumix G 42.5mm F1.7 Sony FE 20mm F1.8G +29 more
OP Mecca66 Regular Member • Posts: 183
Re: Focus Question Regarding Sigma Lens On A7riii

Haven't photographed much action so I can't compare it. But I think the movement inside the lens to find contrast might be what I'm feeling.  I appreciate your response.

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