Quality trouble

[Solon8]

Hello everyone,

I'm using the x264's Slow preset with MeGUI, but I don't know... there's something bugging me.

In the video, the faces or objects that are close to the camera are detailed, clean, looking-good! But when it's in the background, like a person or whatever, then the quality isn't that great, almost grainy, it loses its detail. Beside increasing bitrate, is there a parameter I should try changing for that issue?

I don't know if it's because I'm getting used to the video quality I'm watching, but I did not have this problem a few years ago, with an actually faster preset. I don't get it.