Rods
The rods in our eyes are particularly sensitive to changes in brightness or darkness. Human beings as a species have poorer night vision than other vertebrates. In poorly lit situations, it takes the human eye several minutes to adjust to the change in lighting and focus on an image (Murray, n.d.). Consequently, rods do not allow humans to see detailed and defined images. In fact, these particular photoreceptors are relatively useless in helping us to see color. Unlike cones, rods only contain one type of light-sensitive pigments. So, while rods help humans focus on monochromatic images in low-light situations, they play no role in how we see or perceive color. Instead, rods see images in a gray-scale and are mainly responsible for determining the shape of an object in poorly lit situations (Gouras, 2009).