The viewfinder is (usually) just the raw video stream from one of the cameras in your phone.

When you take the picture, your phone captures an image with multiple cameras (if your phone has them), composits them together, and applies a bunch of black-box post-processing to the image. This step is usually a trade secret as phone makers try to compete for the “best camera”.

After that, it applies any extra user-set filters you may have.

IMO, they’ve taken the processing way too far in the race to make “better” pictures. The newest phones often run the image through a small ML model that tries to extrapolate detail, and personally I think it looks bad.

Marques Brownlee actually did a video about this, and I remember thinking, “Okay, so I’m not crazy!”

I really wish my camera had a “do less” setting.