Dog vision is different from human vision in several ways. They can't distinguish red and green.
And they don't have sharp focus in a central area of the retina. Instead of concentrating photoreceptors in the fovea centralis, which gives us humans very detailed and color-sensitive vision in the pinpoint center of our attention, they have a broader area of focus.
Dog vision may not be as sharp or as colorful as ours, but it's better at tracking fast-moving objects, because their eyes are optimized to respond quickly.
Our photoreceptors have to recharge at a rate of about 60 times per second. This "flicker fusion" threshold is the recharge rate that allows us to perceive a steady image on a flickering source like a TV screen.Watching video that refreshes at 30 or 25 frames per second will pass for stable reality for us—but not for a dog. As dog expert Alexandra Horowitz says, "Dogs have a higher flicker-fusion rate than humans do: seventy or even eighty cycles per second. This provides an indication why dogs have not taken up a particular foible of persons: our constant gawking at the television screen," which is not fast enough for dog vision. "They see the individual frames and the dark space between them too, as though stroboscopically. This—and the lack of concurrent odors wafting out of the television to engage them. It doesn't look real."
Their fast flicker-fusion rate and reaction time also explains why dogs are so good at catching flying frisbees or tossed chunks of cheese.
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From the book: Inside of a Dog: What Dogs See, Smell, and Know
by Alexandra Horowitz
by Alexandra Horowitz
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