What’s the smallest number of photons we need to see?
To yield colour vision, cone cells typically need a lot more light to work with than their cousins, the rods. That’s why in low-light situations, colour diminishes as the monochromatic rods take over visual duties.
In ideal lab conditions and in places on the retina where rod cells are largely absent, cone cells can be activated when struck by only a handful of photons. Rod cells, though ... Read even more
