I always interpreted it more like he could see in a wide range of the light spectrum and so could just see whatever was already being emitted. Like our eyes but better.
That said, he does have the ability to send out rays from his eyes too so maybe it’s more like radar? Not that it needs to make sense anyways…
Swait superman has xray vision? So he could give someone cancer just by looking at them? “If looks could kill…”
I always interpreted it more like he could see in a wide range of the light spectrum and so could just see whatever was already being emitted. Like our eyes but better.
That said, he does have the ability to send out rays from his eyes too so maybe it’s more like radar? Not that it needs to make sense anyways…