Dogs are red-green color blind. They see a brighter
and less detailed world when compared to humans. Peripheral
vision is better than humans (dogs see more of the world), but
distance is not judged quite as well. Dogs excel at night vision
and the detection of moving objects. Figure 1 is a rough guesstimate
of what a dog and human might see when viewing a color band
(the electromagnetic spectrum).
These differences in visual ability make sense
in light of evolutionary theory. Good depth perception and visual
acuity are necessary for a primate (from which humans evolved)
jumping from tree limb to tree limb. Good color vision enabled
this primate to choose the ripest and most nutritious fruit.
The canine, on the other hand, is well adapted as a nocturnal
hunter of camouflaged prey.
Dogs see something like a human deuteranope,
that is, they are red-green color blind (occurs in 4%
of male humans). Simply put, this is due to having only
2 cone types rather than 3 (light sensitive cells
include cones and rods).
2. Detail or Acuity
Since dogs have no fovea (or area with
100% cones), there estimated eye for detail is (roughly)
6 times poorer than in an average human.
3. Night Vision
The have more rods (which
enable night vision).
Dogs have much better night vision for 2
They have a structure called
the Tapetum Lucidum
This is a reflective surface behind the retina (area
including the light sensitive cells) that reflects light back
through it (gives the eerie shine at night).
4. Sensitivity to Movement
Dogs are better able to detect
5. Depth & Field
Figure 2 show the field of
view of a human and a dog. Due to the
placement of the eyes, humans have an
overlap of the field of each eye of 140; in dogs,
it is about 100.
This results in the dog
having limited ability to accommodate (focus on items at
different distances), but a wider overall field allowing
them to see more of the world.