Jumping spiders have four pairs of eyes; three secondary pairs that are fixed and a principal pair that is movable.

The posterior median eyes (PMEs) are vestigial in many species, but in some primitive subfamilies, they are comparable in size with the other secondary eyes and help to detect motion.
While unable to form images,  the reduced pair of eyes is thought to have a role similar to that of insect ocelli by receiving light from the sky.
The photoreceptors in the other secondary pairs are almost exclusively green-sensitive, but the PMEs have two visual pigments different from those in all the other eyes, sensitive to blue and UV light.

The posterior lateral eyes (PLEs) are wide-angle motion detectors that sense motions from the side and behind.
Combined with the other eyes, PLEs give the spider a near 360° view of the world.

The anterior lateral eyes (ALEs) have the best visual acuity of the secondary eyes.
They are able to distinguish some details, as well, and without them, no "looming response" can be triggered by motion.
Even with all the other pairs covered, jumping spiders in a study could still detect, stalk, and attack flies, using their ALEs only, which are also sufficiently widely spaced to provide stereoscopic vision.

The anterior median eyes (AMEs) have very good vision.
This pair of eyes is built like a telescopic tube with a corneal lens in the front and a second lens in the back that focus images onto a four-layered retina, a narrow, boomerang-shaped strip oriented vertically.
Physiological experiments have shown they may have up to four different kinds of receptor cells, with different absorption spectra, giving them the possibility of tetrachromatic color vision, with sensitivity extending into the ultraviolet (UV) range.
As the eyes are too close together to allow depth perception, and the animals do not make use of motion parallax, they have evolved a method called image defocus, instead.
Of the four photoreceptor layers in the retina, the two closest to the surface contain UV-sensitive pigments, while the two deepest contain green-sensitive pigments.
The incoming green light is only focused on the deepest layer, while the other one receives defocused or fuzzy images.
By measuring the amount of defocus from the fuzzy layer,  calculating the distance to the objects in front of them is possible.
In addition to receptor cells,  red filters also have been detected, located in front of the cells that normally register green light.
All salticids, regardless of whether they have two, three, or four kinds of color receptors, seemingly are highly sensitive to UV light.
Some species (for example, Cosmophasis umbratica) are highly dimorphic in the UV spectrum, suggesting a role in sexual signaling.
 Color discrimination has been demonstrated in behavioral experiments.

The principal, AMEs have high resolution (11 min visual angle), but the field of vision is narrow, from 2 to 5°.
The central region of the retina, where acuity is highest, is no more than six or seven receptor rows wide.
However, the eye can scan objects off the direct axis of vision.
As the lens is attached to the carapace, the eye's scanning movements are restricted to its retina through a complicated pattern of translations and rotations.
This dynamic adjustment is a means of compensation for the narrowness of the static field of vision.
It is analogous to the way most primates move their eyes to focus images of interest onto their fovea centralis.
Such movements within the jumping spider's eyes are visible from outside when the attention of the spider is directed to various targets.
Jumping spiders have four pairs of eyes; three secondary pairs that are fixed and a principal pair that is movable.
The posterior median eyes (PMEs) are vestigial in many species, but in some primitive subfamilies, they are comparable in size with the other secondary eyes and help to detect motion. While unable to form images,  the reduced pair of eyes is thought to have a role similar to that of insect ocelli by receiving light from the sky. The photoreceptors in the other secondary pairs are almost exclusively green-sensitive, but the PMEs have two visual pigments different from those in all the other eyes, sensitive to blue and UV light.
The posterior lateral eyes (PLEs) are wide-angle motion detectors that sense motions from the side and behind. Combined with the other eyes, PLEs give the spider a near 360° view of the world.
The anterior lateral eyes (ALEs) have the best visual acuity of the secondary eyes. They are able to distinguish some details, as well, and without them, no "looming response" can be triggered by motion. Even with all the other pairs covered, jumping spiders in a study could still detect, stalk, and attack flies, using their ALEs only, which are also sufficiently widely spaced to provide stereoscopic vision.
The anterior median eyes (AMEs) have very good vision. This pair of eyes is built like a telescopic tube with a corneal lens in the front and a second lens in the back that focus images onto a four-layered retina, a narrow, boomerang-shaped strip oriented vertically. Physiological experiments have shown they may have up to four different kinds of receptor cells, with different absorption spectra, giving them the possibility of tetrachromatic color vision, with sensitivity extending into the ultraviolet (UV) range. As the eyes are too close together to allow depth perception, and the animals do not make use of motion parallax, they have evolved a method called image defocus, instead. Of the four photoreceptor layers in the retina, the two closest to the surface contain UV-sensitive pigments, while the two deepest contain green-sensitive pigments. The incoming green light is only focused on the deepest layer, while the other one receives defocused or fuzzy images. By measuring the amount of defocus from the fuzzy layer,  calculating the distance to the objects in front of them is possible. In addition to receptor cells,  red filters also have been detected, located in front of the cells that normally register green light. All salticids, regardless of whether they have two, three, or four kinds of color receptors, seemingly are highly sensitive to UV light. Some species (for example, Cosmophasis umbratica) are highly dimorphic in the UV spectrum, suggesting a role in sexual signaling.  Color discrimination has been demonstrated in behavioral experiments.
The principal, AMEs have high resolution (11 min visual angle), but the field of vision is narrow, from 2 to 5°. The central region of the retina, where acuity is highest, is no more than six or seven receptor rows wide. However, the eye can scan objects off the direct axis of vision. As the lens is attached to the carapace, the eye's scanning movements are restricted to its retina through a complicated pattern of translations and rotations. This dynamic adjustment is a means of compensation for the narrowness of the static field of vision. It is analogous to the way most primates move their eyes to focus images of interest onto their fovea centralis. Such movements within the jumping spider's eyes are visible from outside when the attention of the spider is directed to various targets.
Jumping spider