Our eyes are comfortable until we get to around 3,500 lumens. When the brightness of the direct or reflected light gets to about 4,000 lumens, our eyes begin to have difficulty absorbing the light. To reduce the discomfort caused by the amount of light entering our eyes, we squint. Once you get to around 10,000 lumens, your eyes are so bombarded that they begin to completely block out the light. Prolonged exposure to light of such intensity can cause damage resulting in temporary or even permanent blindness.
Visible light is light that can be perceived by the human eye.
When you look at the visible light of the sun, it appears to be colorless, which we call white. It is made up of many color frequencies. There are two basic ways by which we can see colors. For example, to see a yellow object, either the object is directly emitting light waves in the yellow frequency, or it is absorbing the blue part of the spectrum and reflecting the red and green parts back to your eye, which perceives the combined frequencies as yellow. When we talk about light in reference to sunglasses, three types of light are important.