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The rods provide achromatic (non-colour) vision in the range of illumination levels from 10-6 to 10 cd/m2, whereas the cones provide chromatic (colour) vision in the range 0.01 to 108 cd/m2. In other words the human eye is capable of detecting illumination levels with a difference of 1014 or 100,000,000,000,000 times! However, the neural units processing the signals to the brain are not capable of transmitting a signal with this complete dynamic range.
But the point is that the eye adapts to the average light level present. This adaptation is to some extent dynamic, but when the light level changes too fast the eye becomes momentarily blinded.
Turning on the light in a completely dark