Elven physiology and darkvision

Elves maintain an inherent connection to the weave, so much so that they can come to see the weave with the naked eye. As the elves grow they are taught by their elders and spend hours upon hours training to watch how the weave interacts with the world around them. You would have been taken to a river to observe the flow and understand its movements. Taken to a dark cave to observe people moving in the darkness and see the interactions the weave makes with both the living and non living. These bits of training move on to all kinds of phenomena, down to finally viewing a bonfire, observing the flame and then the cinders as they float through the air. Once you can track the individual cinders and predict their flow, you move on to the smoke and then the very air around it. This process takes decades to perfect with most elves not truly attaining skill untill their first century. Once this skill is learned an elf can see forms and shapes in the dark, differentiating heat and shape, but unfortunately no colour.
This process takes incredible focus and attention to detail. Elven eyes are able to focus intensely, on tiny details, and the mind of an elf is also able to maintain intense concentration for extended periods of time. An elf could focus on something to the extreme of being oblivious to an explosion nearby. This can often perpetuate the view that elves are aloof and indifferent towards other races. In addition to the eyes ability to view some of the weave, the brain itself can absorb elements of the weave to. In doing so it shares a continual connection with other minds that seem to be on almost the same wavelength. It is said elves can almost sense the presence of other elves and it is a comforting feeling, like that of warm hug as they find connection with other elves. They believe in community and working together for the good of society. It is said that during a casting of high magic, all elves open their minds and share a huge and open telepathy network. It is also this ability to absorb and interact with the weave in addition to their fey lineage that offers their mental protection from magical charms and sleep effects. 
Some would theorise that in a world of dead magic or a total anti magic area would not only shut down an elves darkvision, but their resistance to charm effects as well. The loss of the essence of the fabric of life could even go so far as to slowly erode the minds of the elves, sending them into madness...