Weird Screen Fade In/Out

So when playing a world in minecraft, some weird thing starts to fade in on my screen, some time it goes, some time it stays for a couple seconds. The screenshots are when I was in spectator, and took a screenshot in front of white concrete to see what it was. And, the screen shots with the markings, each happened on a different world. Also, when going underground in spectator, or just breaking blocks, my screen starts to dim real fast, even with night-vision, and it only goes back up when I'm above ground. This has happened on several worlds, but I got out of minecraft and I haven't been in since.