How do I prevent the auto-focus from bouncing on my Galaxy J7 smartphone?

Question

I'm trying to film myself in a dark room with videos. When I start the camera, it records as expected: it checks focus and stops on a nice and crisp view.

However, as I record every second or so, even if nothing changes, it runs the auto-focus feature. That means the video "jumps" (zoom in/out for a little while). It's very visible on the final video.

Is there a way for me to setup the camera so that it doesn't re-auto-focus all the time?

My phone is a Galaxy J7 (SM-J700T).

I've seen many options to change the lighting, colors, etc. but I don't recall seeing anything about auto-focus. I'm hoping I may have missed something so I can use the phone camera without having that bad side effect.

Answer 1

Okay, I found the answer.

After I start recording, I can click for a second or so on the screen where I want the focus to be. The camera is going to make that item appear in focus and then block the focus to that point until I cancel it.

There should be an (AF) button appearing on the side. Clicking that button allows to go back to the auto-focus mode.

Note that there seems to be two modes: one when you do this when you're not recording and one when you are already recording. At this point I have not found the real difference, but the items (buttons) appearing on the screen are different. So I would imagine that there is some kind of a difference between both modes.