Dogs have excellent night vision, a trait crucial to their predatory ancestors. The minimum threshold of light dogs require for vision is about five or six times lower than that of humans. So your pooch won't be stumbling around in the dark if you don't leave a light on for him.
Unlike our eyes, a dog's eyes are designed to function well in low-light conditions. Both canines and humans (and many other animals) have two types of light-sensitive cells in the retina called rods and cones. These cells respond to light and process visual information, which is transferred to the brain for interpretation. Rods work best in dim light and can detect motion. Cones are used in bright light to detect color and details.
The retinas of dogs are dominated by rods, allowing them to see very well with very little light. They can also sense small motions, which helps make them good hunters. However, dogs have about one-tenth of the cones that humans do, so they don't see color in the same way we do. |