The hunt for focus starts close to the camera and works its way out. If there are twigs in front of the subject and they fall within the focus box, they will trigger focus lock. You want the subject to be the first thing that triggers focus lock so you want to keep twigs etc out of the focus box until the subject has triggered the focus lock. If you're using S mode the camera will keep the first focus lock but in C or A mode, something closer falling within the focus box can get the focus point to change, even if the subject hasn't left the focus box.

If you got a lock on something that you didn't want to be the focus point you just need to take your finger off of the shutter release button and the process is then free to start again. In S mode you can get the focus lock as described and then recompose (while holding the shutter release button half way to keep the focus lock) to get the framing the way you want it. In C or A mode you can't get that sort of control over what the camera selects as a focus point, and any attempt to recompose could trigger another (unwanted) focus lock.

If you were using C mode it would be prone to changing the focus point, even after achieving a perfectly good focus lock on the subject. The mystery is how were you getting away with it before? With S mode the camera keeps the first focus lock until you either take the shot or take your finger off of the shutter release button.

I use that technique when I'm using hyperfocal distance. I can get a focus lock in one direction and then recompose to point in a totally different direction and the camera will keep the focus lock until the shot is taken.

Shooting at a high frame rate with subjects in a complex situation like this is your friend. My wife has this camera but I don’t recall whether it has the ability to customize the buttons. With my Sony A1, I can customize a button with a specific AF mode associated with that button. For the most part, I set that button for “spot” af and use that button for focusing when your subject is surrounded by clutter like the branches in your photo. Using a wider AF mode, like “wide” or “zone” you camera can get confused on what to focus on which is what has happened here. There should be work arounds, you just need to get a better understanding of the capabilities of your camera. Good luck and have fun. You have a nice little camera there.

Yesterday while out taking photographs I saw an Osprey sitting in a tree. He was maybe 30 yards away from me and I took pictures while resting my arms/camera on the window of my truck. Out of a few photos I took, the first two were in sharp focus. The others were completely out of focus. Even though my green focusing box was lighted up when placed on the bird, I could see the photo was not in focus. But there was the focus box saying OK so I took the picture.

When I got home and saw the photos only the first two were in focus. Looking at the other out of focus photos revealed a branch in front of the bird that was in sharp focus. The camera, a Sony RX10IV, had focused on a tiny branch in front of the bird but not the bird itself. I understand that but am not understanding why, when I saw the bird was not in focus and I did move the camera around in a circle to once again get the bird in focus, it did not work.

I suspect this is somewhat of an anomaly but not a happy one for me. I have noticed when doing macro subjects using the 600mm range of the lens that occasionally the same thing happens. The insect is in sharp focus for a couple of shots but not in others when the focusing square seems to be in the same place.

Any ideas or suggestions? This morning I went to a spot metering box to give it a try.

Dennis