Legolas is a fraud… unless light travels differently in Middle-Earth compared to the way it does in our world.
Of course it’s fiction, but if we’re going to get scientific about it…is anyone familiar with elvish occular anatomy? Perhaps their eyes have something ours do not, or perhaps they evolved differently. /shrug
Or you know, magic?
Some of those elves can see the future, seeing something far away shouldn’t be that hard?
From all the literature I’ve read about elves – so this isn’t specifically Tolkien oriented – their eyes are different than standard humans. They are able to see a wider spectrum than humans, their eyesight is keener, think along the lines of a hawk or eagle but not so magnified. Typically, literature describes elves as having almond shaped eyes, like oriental but I think the shapes are different to account for this difference in viewing.
Elves are also typically depicted as very observant with heightened senses, impeccable archers/snipers, and almost always coming from forest environments. So, this can be translated to eyesight that not only see a portion of UV and infrared but is tailored for noticing slight movements and color differences within a forest canopy (a generally darker environment) and can focus quickly between near and far distances with clarity and accuracy.