The anatomy of low light —

Human beings have a natural fear of the dark. Human beings depend primarily on sight as a means of figuring out what is going on in the world around them so it should come as no surprise that we naturally find conditions where this sense is significantly diminished or useless to be extremely disconcerting. Our eyes are remarkable organs capable of incredible feats, but seeing in the dark isn’t one of them. As a species our night vision capabilities are some of the worst you can find on the planet….certainly the worst you will find among top level predators.

Our night vision depends on photoreceptive structures in our eyes called “rods” that have a pigment called rhodopsin which is sensitive enough to be triggered by as little as a single photon of light under ideal conditions. Unfortunately our rods have a saturation point, a point at which they essentially white out and our cones (the structures of our eye responsible for vision in daylight and perceiving color) take over. If our rods are exposed to too much light they become essentially useless for a brief period of time, and it takes as long as 30 minutes for them to “recharge” to the point where you regain your peak night vision capabilities. All of us have at some point gone from a place where there is abundant light into a place that has almost no light and we’ve all found out that it takes us a couple of minutes in the dark for our eyes to adjust so we can actually have some idea of what the environment around us is like.

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