The vision of the dog differs from that of the man by four main characteristics:
- Colors: Contrary to popular belief, the dog does not see black and white. His vision spectrum is just much narrower than ours. It is limited to yellow and blue for a result that is closer to a monochromatic vision than a colorful vision.
Visual acuity: In dogs it is generally lower than in humans. On the other hand, his night vision is far superior to ours (5 times less light is enough for him to move effortlessly in a hilly environment). Proud to descend from the wolf, nocturnal hunter par excellence, the dog is able to distinguish a moving prey by means of the only light emitted by the stars. We find this same capacity in the cat. This anatomical feature is due to a fluorescent film (tapetum lucidum) that covers the bottom of the retina and acts as a light amplifier. This film causes the "fluorescent eyes" appearance of dogs at night. Note that all dogs are presbyopic and very poorly see the details less than 25 cm.
- The field of vision: It is more important than ours. This characteristic is variable depending on the breed, the shape of the skull, the mouth and especially the position of the dog's eyes. But the zone of coincidence (zone of natural vision of the relief) is thus weaker.
- The frequency of vision: It is much higher than ours. We see a maximum of 16 frames per second (early frequency of amateur cinema when movements seemed jerky). At 24 frames per second (25 for television) we perceive images as a continuous movement, without separating them from each other. By increasing the frequency of vision, cinema for example, it turns to 50 frames per second to get, at projection, a slow motion. We decompose much better movements on these famous "slow motion" cinematographic that correspond to a canine vision. Consequence: a dog is sensitive to a human movement to 1.5 km while he will not distinguish anything from a motionless object to 20 m. He will see television a series of jerky images unrelated to each other. No telephage, the dog … This high frequency gives the dog a reaction time faster than ours.
In conclusion: the dog sees less well with his eye than the man (in sharpness and in color, not in speed nor in field). But let's imagine that we talk about the dog, about perception instead of vision. The dog hears much better than us (with a higher bandwidth), feels incomparably better (with a palette of odors a hundred times larger) and we can even imagine another meaning that we would have lost completely (it is difficult to understand how these animals , deported more than a hundred kilometers, find their niche). With these three senses, at least, the dog creates a kind of instant map of his environment that allows him to navigate in all circumstances, to hunt effectively for food, to predict the dangers, in short to easily evolve in the world that surrounds. Human vision is no longer combined with other senses because we isolated it, thinking that the eye was functioning as an optical instrument. Our perceptions of the environment today are almost exclusively visual. It is not the same in the animal world, where different senses are combined to create a representation of the biotope which, if we believe their ability to survive, is well worth ours.