Your turn
Each lab is one step from the video. Change things and see what happens.
Each lab isolates one part of the story. The models are simplified to show the idea.
Tap the buttons and slide the sliders.
Drag the line across the park. What happens to the red ball on the green grass?
Sweep the split across the scene. Which hues survive the dichromat model, and which merge?
Tap Dog eyes. Can you still see the red ball?
A simulation of dog colour vision and sharpness; nobody can see through a dog’s eyes, so treat it as a guide.
Flip to dog eyes. Which toys still pop out of the grass?
Compare the six toys in both views. Why do red, orange and green converge?
Tap Dog eyes. Which balls are easy to see?
Move the squirrel far away, then set it running. When does the dog side lose it, and when does it pop out again?
Increase the distance on the dog side, then add motion.
Slide the squirrel far away. Then tap Run!
Extra blur on the dog side illustrates lower sharpness (about 20/75 vs normal human 20/20). Motion is marked, not modelled.
Slide toward night, then switch the mirror layer off. Who sees more of the park?
Lower the light and toggle the tapetum. How does the dog side change?
Slide to night. Who can still see?
A picture of the idea: the brightness difference is illustrative, not measured.
Drag the squirrel around the dog. Where do both eyes see it? Where is the blind spot?
Move the target through the binocular zone, the side fields and the blind spot.
Slide to dog eyes, switch to dusk, then tap the red ball when you find it.
Blend the two visual systems, then compare day and dusk.
Slide to dog eyes. Then tap Dusk. Can you find the red ball?
Colour, blur, width and brightness are rough approximations of dog vision.
Dogs see the world in their own way. They see fewer colours than you. Things look a bit blurry. But dogs are great at spotting things that move, and they see well in the evening.
Throw a red ball on green grass. Your dog may run right past it! To a dog, red and green look almost the same. So the ball hides in the grass. Your dog finds it with its nose.
Your eyes have three kinds of colour helpers. A dog has only two. So a dog sees blue and yellow best. Want a toy your dog can spot? Pick a blue or yellow one!
Dog eyes are not as sharp as yours. A dog has to come much closer to see small things. But movement makes something much easier for a dog to spot.
Dog eyes have a mirror inside. Light bounces back, so the eye gets two tries to catch it. That is why dog eyes glow when a light shines on them.
Cats see a bit like dogs. Watch how cats see!
Dogs see the world in fewer colours, less sharply and much wider than we do, and they see better in dim light. They have two kinds of colour-sensing cells (cones) where we have three, so their world is mostly blues, yellows and greys.12 Their eyesight is about 20/75 instead of our 20/20,7 but they take in roughly 240 degrees around them compared with our 180,7 and a reflective layer at the back of the eye helps them at dusk.8 On top of all that, a dog's nose does a huge share of the work.14
Scientists sum it up like this: dogs lose to us on colour, sharpness, close-up focus and how much the two eyes' views overlap, and probably beat us in dim light, field of view and spotting flicker and motion.4
Colour vision starts in the retina, the thin layer of light-sensing cells at the back of the eye. The cells for colour are called cones. People usually have three types, often called red, green and blue cones.9 Dogs have only two: one most sensitive to blue-violet light (around 429 nanometres) and one most sensitive to yellowish-green light (around 555 nanometres).13 Scientists call this dichromatic ("two-colour") vision.
With two cone types, a dog still sees colour, mostly as blues and yellows. What it can't do is tell red from green: both land on the same yellowish cone, so they look like similar dull yellowish browns or greys.111
Here is roughly how some everyday colours shift (a simple simulation; nobody can see through a dog's eyes, so treat it as a guide):
Partly. Their colour vision is very like a strong form of the most common human colour vision deficiency, red-green colour blindness, in which people find reds and greens hard or impossible to tell apart but still see blues and yellows.10 In 1989, researchers trained three dogs to pick the odd one out among coloured lights and found exactly two cone types.1 In 2017 an Italian team showed dogs a moving coloured target hidden in a pattern, like the dot tests eye doctors use, and the dogs responded just like red-green colour-blind people.2 Another study found that when dogs could choose between using colour or brightness, they used colour.3
This is why a red toy on a green lawn is so easy to lose: to a dog, the red ball and the green grass are almost the same colour.11 If you want a toy your dog can spot, pick blue or yellow.11 (Your dog will probably still find the red one with its nose.)
No. This is one of the best-known pet myths. It was spread by a 1937 dog-training manual that guessed the world looks like "varying highlights of black and gray" to dogs.11 Since then, careful experiments have shown that dogs do see colour, just fewer colours than we do.13
Less sharp than ours. Veterinary eye doctors usually put a typical dog at about 20/75: a detail a person with normal sight can make out from 75 feet away, a dog has to come within 20 feet to see as clearly.7 In a 2017 lab test with striped patterns, people could spot the stripes from roughly three times farther away than dogs, in both bright and dim light.5 Dogs also can't focus as well close up.47
Eyesight also varies by breed. Many long-nosed dogs have a horizontal band of sharp vision across the retina called a "visual streak", while short-nosed breeds like pugs have a smaller central spot instead.5
What dogs lack in detail they make up for in noticing movement. Working dogs have been reported to recognise moving objects about 810 to 900 metres away, but still objects only at about 585 metres.6 That's why a dog may ignore a squirrel frozen on a branch, then launch the instant it twitches.
Not in complete darkness, but they see much better than we do in dim light. There are three reasons:
The tapetum is also why dogs' eyes glow when a flashlight or camera flash hits them: that's the light bouncing back out.13 Even so, dim light costs dogs detail too; in the 2017 test their sharpness dropped at night just as ours did.5
| People | Dogs | |
|---|---|---|
| Colour cones | 3 types (trichromatic) | 2 types: blue-violet and yellow-green (dichromatic)1 |
| Colours | Full rainbow | Blues, yellows, greys; red and green look alike2 |
| Sharpness | 20/20 | About 20/757 |
| Field of view | About 180° | About 240° (roughly 200–250° by breed)715 |
| Both-eyes overlap | About 140° | About 30–60°16 |
| Dim light | Weak | Much better: more rods, tapetum, big pupils8 |
| Motion | Good | Excellent46 |
A dog's eyes sit more toward the sides of its head than ours do, so its view wraps much farther around: about 240 degrees on average, compared with about 180 for people.7 Researchers report a range from about 200 to 250 degrees depending on skull shape, with long-nosed breeds at the wide end.15
The trade-off is the zone that both eyes see at once, which helps judge distance. In dogs it's roughly 30 to 60 degrees; in people it's about 140.16 So your dog is great at noticing something off to the side, while your two eyes share a much bigger overlapping view, which helps with judging distance.
In 2022, Cornell veterinary researchers scanned the brains of 23 dogs and found large nerve pathways running from the smell centre straight to the occipital lobe, the part of the brain that handles vision. This link had never been documented in any species before.14 It fits what vets see every day: blind dogs can still play fetch and find their way around remarkably well.14 For a dog, smell and sight work together to build a picture of the world.
Mostly blues, yellows and greys, a bit blurrier than ours, and wider. Reds and greens look like dull yellowish browns. A dog notices movement very quickly and sees better than we do at dusk, but fine detail is harder for it.
No. That's an old myth. Dogs have two types of colour cones (we have three), so they see colour, just fewer colours. Their colour vision is similar to a person with red-green colour blindness.
Blue and yellow. A blue or yellow toy stands out clearly on green grass, while a red or orange toy blends in, because red and green look similar to a dog.
Not in total darkness, but much better than us in dim light. Their retinas are packed with light-sensitive rods, their pupils are large, and a mirror layer behind the retina (the tapetum lucidum) bounces light back for a second chance. Details still look blurry.
It depends on whether things move. Working dogs have spotted moving objects about 810 to 900 meters away, but still objects only at about 585 meters. For fine detail, a dog needs to be about three times closer than a person.
A reflective layer behind the retina, called the tapetum lucidum, bounces light back out of the eye. When a flashlight or camera flash hits it, the eyes shine. People don't have this layer.
They can see screens, but differently: fewer colours, less fine detail, and dogs focus less well up close than we do. Movement on a screen can catch their attention.