Cones
Cones, however, are not as sensitive to light as rods and do not saturate except in the case of intense light (Longstaff, 2011). Therefore, cones are only functional in brightly lit situations (Murray, n.d.). Cones respond to various frequencies of light entering the eye (Gouras, 2009) and pick up on one of three types of color: green, red, or blue (Murray, n.d.). People who are classified as color blind either lack a specific color-sensitive cone or have weakened cones in their retina (Gouras, 2009). Cones are primarily located in a central part of the retina called the macula (Murray, n.d.). Within the macula, is the fovea which is an area of the retina that consists solely of cones and no retinas (Murray, n.d.). When humans attempt to focus for a period of time on a particular image our eyes rely on the fovea part of the retina for the fine definition of said image (Murray, n.d.).