From what we've heard so far, there is gonna be a pretty big camera upgrade in the standard iPhone 15 and 15 Plus models. The sensor is set to not only jump from 12MP to 48MP but according to Live Mint it looks like it may feature a stacked CMOS sensor which won't be present in the Pro models.
A stacked image sensor will enhance the camera's performance allowing for more noise reduction, brighter image rendering, more detail and overall better quality photos but we won't be able to tell how much better it'll really be until we get the phone in our hands.