Why is my phone keeps brightness keeps changing

[Android Central Question]

So I been using my new phone I got for Christmas and I have my brightness at 100% and my auto change brightness off and it still keeps getting dimmer then brighter

 

[EskayPLYZ]

My phone does the same, depending on what's on the screen, the brightness changes to where it looks as if it's flickering. Can get annoying and distracting