The receptor is a biological transducer. Receptors share certain features with neurons. Like neurons, they have a resting potential, they also depolarize when stimulated. The depolarization is know as a generator potential. The actual process by the brain converts the impulses transduced by receptor cells into sensations is know as coding.
Visual capacity varies considerably among different species.
In very simple animals, such as certain inserts. Humans can do much more than simply response to the present of light. The detect shapes, follow movement, differentiate among colors, and use vision to judge distances. They may not see as well as some animals but no other animals have as versatile a visual system or can absorb as many types of visual stimuli. All visual sensations are produced by the relative differences in length, amplitude, and purity of the light waves.