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Why can dogs only see red?
Question Date: 2003-05-29
Answer 1:

Well, the information I found tells me that dogs see colors different from us and that they do not see the color red. The color vision is controlled by cells in the retina of the eye called cones. The dog does have cone cells in its retina, that means they can see color. However, the cones make up only a small percent of the cells in the central area of the retina of the dog (less than 10%). In human, the central area contains nearly 100% cones. Experiments on the dog's eye show that the dog can probably see shades of blue, yellow and gray. Since it cannot see shades of red, the dog is said to have dichromatic (two color) vision compared to people who have trichromatic (three color) vision and can see the full spectrum of colors.

For a dog, this is probably not important. They can use other visual clues such as brightness and position of objects, and their other senses like smel, taste and texture.

Dogs also don't see fine details as well as humans. We usually see 20/20, but dogs see about 20/80. That's four times blurrier! Dogs do see better at night, though, and they also see moving things better than we do. That is why a dog can spot a moving ball that you throw even if it is in the woods. He can tell exactly where it stopped moving.
Hope this helps answering your question.

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