For a long time we thought dogs saw the world only in shades of grey, but we are learning more about a dog’s eyesight.
Eye retinas are made up of rod and cone receptors. Cones control color discrimination and require bright light. Rods work better in dim light. Dogs have more rods and as a result they can see better in the dim light than humans. They may need only about a quarter of the light that humans need. This has served them well as predators.
Their eyes also have a reflective layer that helps even more to see in the dark. We see this reflection when a light shines on their eyes or when a flashbulb is used to take their picture.
They do lack the numbers of cones humans have and cannot tell the difference between, say mauve and dusty rose. But then most straight men can’t either.
The chart below shows how dogs and humans see color.
It is unfortunate that most pet toys are colored red, safety orange, or bright chartreuse, colors a dog cannot distinguish. While humans can easily see a red ball in green grass, a dog is trying to find a brownish object in a grayish setting. Yellow and blue would be better choices for a dog toy.
On average dogs have 20-75 vision. That is, they see at 20 feet away what a person with normal vision can see from 75 feet away. However, dogs can distinguish movement at great distances. Some dogs, such as police dogs, have the ability to see a moving object almost a half mile away.
Of course some breeds have better vision than others. It would be safe to say that Greyhounds, Poodles and other sight hounds (yes, they are) have better far vision than a Beagle or Basset Hound. A Bloodhound tracking has little use for vision. In fact it would probably be a distraction.
Whenever we walked her, we always got the same boring question:
How does he see?
We always gave the same smartass answer: