The main pair of eyes in jumping spiders even sees in colour.

The thing that gets me about invertebrate vision is how much less brain they’re using for signal processing.

Humans (mostly) have three colors of cones in our eyes, red, green and blue. Comparing the relative values of signals from these three colors allows us to experience color vision. The (mostly) is allowing for colorblindness or the ten or twenty tetrachromats out there. That takes a lot of signal processing, and us humans use more weight in brain matter to do that processing than a lot of seeing organisms entire bodies.

We can talk about the human eye in terms of the optical power of the lens, the dot pitch, “resolution” and frequency response of the retina etc. but my meat GPU takes that raw data and presents to my consciousness an apparently continuous 3D color representation of my surroundings. I’ve got real-time reverse ray tracing; I can look at a reflection in a shiny object and compute the reflected object’s shape and position in the world, and recognition of my own reflection is done in hardware.

No arthropod on earth contains as many neurons as I’ve got in my occipital lobe. What do they “see?”