On the back of your eye is the retina. This is where the image is produced. It is made up of two kinds of cells called rods and cones . Cones are sensitive to the amount of light entering the eye. They transmit to the brain the brightness of the image.
Rods are sensitive to color.
They transmit the colors to the brain. Between the two, you brain will process these impulses and produce a colored image of the light entering your eye. In the front of your eye is a lens with a pupil . The lens focuses the incoming light on the retina. The pupil opens and closes to let more or less light in to the eye.