Rod photoreceptors detect rapid flicker.
It is widely believed that human rods cannot detect rapid flicker. With rod-isolation techniques, however, light-adapted rods detect flicker frequencies as high as 28 hertz, and the function relating rod critical flicker frequency to stimulus intensity contains two distinct branches. Human rod vision may, therefore, depend on two independent mechanisms.
D003623:Dark Adaptation; D005425:Flicker Fusion / Q000502:physiology*; D006801:Humans; D010786:Photoreceptor Cells / Q000502:physiology*