By disecting the eyeball of a dog, researchers found that about 10% of the photoprecepters are cones. Cones are responsible for helping the brain detect colors. The photoreceptors in our eyes are 100% cones. This means that we can process all the colors and see them more vividly. A dog can’t tell the difference between red, yellow, orange, or green but they can see whites light blues, purples and different shades of grey.
Besides just the cones, there are other photoreceptors known as rods. Rods can only detect black and white, but they also process movement extremely well and help to see in the dark. A dogs photoreceptors are mostly rods. This means they can see exceptionally well in low light conditions and see different shades of grey to a higher degree than we can. They can also differinciate the tiniest movements you make. If you’ve ever stood still with your dog in the back yard at night in a shaded area, and caught him by suprise, your dog has probably barked at you. This is because while you are standing still, he doesn’t know who you are. Once you move, even wiggle your finger, he knows its you. This is helpful to an animal that hunts in the dark! On top of having an eye full of rods, they also have a reflective layer that helps to reflect light, helping them to see even better in the dark. This reflective layer is the glow that we see when we shine a light on a dogs eyes in the dark. As a matter of fact, it is believed that a dog can see in 4 times lower light levels than we can because of this reflective layer.
Another thing that comes into factor when talking about a dogs vision abilities is that they can see 240 to 250 degrees around them without moving their eyes. Our field of vision is only 180 degrees. So even if you are standing diagonally behind your dog, chances are he sees you.
Even though dogs are able to see all of these different things with their eyes, vision is not their primary sense. Actually, dogs are considered nearsighted. They really don’t trust their eyes as much as we trust ours. Instead, they trust their sense of smell. To them, the phrase "follow your nose" is a way of life. I’ll write more about that in another blog entery.
So what about T.V.? Do dogs enjoy watching T.V.? Well, T.V. is a series of flickering pictures that are streamed together to make a moving picture. The pictures are broadcast at a rate of about 60Hz, which is how fast they need to move for us to see them as a moving, flawless picture. To a dog, watching T.V. is a lot like watching and old scratchy silent film because their flicker fusion seems to occur at a rate of 70 to 80Hz. So they see the pictures flicker slower and there for it seems choppy to them. So chances are that if your dog likes to watch T.V., it’s probably because of the sounds. Hearing is a dog’s secondary sense, and I will discuss that in another blog entery.
So there you go. You now know the basics of how a dog sees his world. Keep in mind that this is usefull information to have in the training field. Because dogs are so adapt to detecting movement, they often respond to hand signals better than to voice commands. It’s a good idea to teach your dog both. I hope you feel closer to you canine friend now that you understand a bit better how he or she precieves the world.