That’s because the cones in the centre of our vision are less sensitive to light as they only each capture a certain wavelength. The rods which are more prevalent in our peripheral vision on the other hand, capture a much broader spectrum and are thus a lot more sensitive to brightness variation at the cost of only seeing the world in black and white.
Interesting that it is more visible when not looking directly at it.
That’s because the cones in the centre of our vision are less sensitive to light as they only each capture a certain wavelength. The rods which are more prevalent in our peripheral vision on the other hand, capture a much broader spectrum and are thus a lot more sensitive to brightness variation at the cost of only seeing the world in black and white.