system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do HD tv's make acting seem so different and often make movies look like home videos?

I noticed this when my parents bought a new HD tv a few years ago... but now I seem to have gotten used to the tv, and actors appear normal on it again... weird...
gpt
Many modern HDTVs have a featured called "Motion smoothing". It was introduced to reduce motion blurring that occurs on LCD displays.  When this feature is on, the TV is creating and inserting additional in-between frames into the video by interpolating the differences between the frames.  A movie traditionally only has 24 frames per second.  This motion smoothing adds frames making the movie to appear to have a higher frame rate closer to what you get from traditional video equipment used for television broadcasts which is between to 30-60 frames per second.  Thus, this is sometimes called the "soap opera effect".  You can typically disable this feature on your TV.