Here's a well-known myth about dog vision: that dogs only see in black and white. While dogs certainly don't see the same range of colors that humans do, they can see some colors. Dogs basically see the world much like how people with red and green color blindness do.
There are actually a number of similarities between dog vision and human vision. For one thing, both dogs and humans have two kinds of color receptors. These color receptors are what we call rods and cones. Rods deal with peripheral vision, how well we see at night, and how we perceive brightness as well as shades of gray. Cones, meanwhile, deal with color perception. Humans have three cones, each of which can detect a specific wavelength of life.
Because we have three cones, we are able to see the differences between hues. Dogs, however, have only two cones, much like people with red and green color blindness.
If you're a fur parent yourself and are curious about how your dog sees the world around it, you might want to check out Dog Vision. This is a web app that can give you an idea of what the world looks like to a dog. All you need to do is upload a photo, click “Process”, and wait for the new image to appear. This new image will show you what a dog would see if it looked at the original image you uploaded.
As you'll notice, dogs don't see as well as humans do. They see far fewer colors, and the colors they do see aren't that rich or vibrant. However, it gets worse. Dogs are also more nearsighted than humans are. A visual acuity test custom-made for dogs put dog vision at 20/75, which is far from the perfect human visual acuity of 20/20. This means that something a dog can barely make out at 20 feet away is identifiable at 75 feet for a person with 20/20 vision.
If you want more information on how dogs see the world compared to how humans see the world, check out this study. It has more details on things like sensitivity to motion, sensitivity to flickering lights, and depth perception in dogs.
Dogs don't see very well, that much is clear. However, that doesn't mean that they're not fully experiencing what the world has to offer. After all, they do have that nose that allows them to gather quite a lot of information about the outside world. A dog's sense of smell is famous for being quite great, though recent studies have pointed out that a human's sense of smell may rival that of a dog's.
In any case, dogs certainly don't have to completely rely on their vision. Plus, even though dog vision isn't that good, dogs can still glean a lot of information from what they see. Sure, the lines dogs see may be fuzzier, and they probably don't perceive as many details. However, combined with their other senses, their vision certainly doesn't leave dogs lacking.
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