Sony FE 24mm 1.4 GM continually focusIng, back focusing, jumping

Started Aug 13, 2020 | Discussions thread
ZilverHaylide Senior Member • Posts: 1,224
Re: Sony FE 24mm 1.4 GM continually focusIng, back focusing, jumping

billorg wrote:

I have a lifetime of experience with cameras and lenses of all kinds, so I am pretty sure when something isn’t behaving correctly. However, I just wanted to run this past you. Brand new lens, first time using today on a NEX 5n which is my smallest travel setup. That means an APS-C sensor with a full frame lens. I use A mount lenses from Sony and vintage Minolta w/adapter as well as manual Zeiss rangefinder lenses if I want to go really small. Anyway, since this 24mm is an F Mount lens, I don’t have to use the adapter.

The lens is hunting for focus far and wide, nothing like my other AF lenses on this body. Some of the pictures are backfocused badly which I haven’t seen my cameras do in years, including my full sized full frame dslr’s from Sony, Canon and Nikon. It is also jittering in and out a short distance (not trying to focus, just jittering when your finger is down on the shutter after it’s in focus). Lastly, it’s acting as if it’s in continual focusing mode, but the camera is set to single shot. The few pics it got right are razor sharp, but I think there’s something wrong with the lens. Has anyone ever experienced problems like this with a defective lens? Thanks, Bill

No experience with either that specific lens or camera, but it almost sounds like the camera and lens are "fighting" each other, in other words, like there is some sort of algorithmic firmware incompatibility between lens and camera.

Considering how much older the Nex 5n is compared to the 24mm f/1.4, firmware incompatibility seems quite possible. Also, isn't the 5n only contrast detect, not phase detect? If so, then acting like CAF mode, cuz that's effectively what it's using?

Have you updated the firmware on the camera? I'd give that a try. But even that might not work, because Sony might have stopped issuing updates for cameras that old. If you live near a retail store or know anyone with a newer body, perhaps you can pair your lens with that in order to know if there's anything wrong with the lens (beyond possible old body incompatibility).

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