Human retina

The retina is a curved screen where light energy changes to into electric impulses that travel to the brain for processing. It has rods and cones that are known as photoreceptors. 

Rods are sensitive to dim light, while cones are sensitive to bright light. 

Furthermore, the structure of retina is pretty simple. The retina contains macula and fovea in it. The macula is just a concentration of cone cells whilst the fovea is a small “pit” on the macula that only contains cone cells. These photoreceptors are the main characteristics that help the retina form an image. 

After an image gets formed on the retina, what the retina does is send an inverted image through the optic nerve and that inverted image travels through from the optic nerve to the brain. Any of the neurons in the visual part of the brain respond specifically to edges orientated in a certain direction. From this, the brain builds up the shape of an object. Information about the features on the surface of an object, like colour and shading, provide further clues about its identity. Objects are probably recognised mostly by their edges, faces and by their surface features.The brain than makes sense of what the image is and flips the image to the correct orientation. Remember, this all happens in a blink of an eye.