I just wrote a big post about cephalopod eyes, and then realized that I had neglect to show any real-life pictures of cephalopod eyes. This blog seems to be getting a bit dry, so let's take some time off and just gaze at some of our beautiful, squishy friends. All images are from the wikimedia commons and have been under a creative commons license.
(Photo by Parent Géry) This guy is Octopus vulgaris, also known as the common octopus. It the most-studied octopod. You can see the slit-shaped pupil clearly.
(Photo by Theasereje) Here's a body shot of another O. vulgaris. Notice how they can look at you with both eyes at the same time - they have the capability for binocular vision. Octopuses, however, prefer monocular vision, and will always use just one eye to sight their prey during an attack (for more info, see this "Lateral asymmetry of eye use in Octopus vulgaris" by Byrne et al.)
(Photo by Elapied) Here we have another gorgeous shot of O. Vulgaris peering out of a hideout with one eye.
(Photo from www.opencage.info) This is an ocellated octopus, O. ocellatus. Besides being very cute, as he peeks out from the shell, he is probably using his mostly monocular vision to monitor his whole environment for danger.
(Photo by Jens Petersen) Here is Amphioctopus marginatus, the coconut octopus, showing us how it can focus both eyes on the same area of space, even if it usually doesn't like to.
By now, you're probably tired of octopuses. Let me give you a break then, and venture into the world of cuttlefish and squid!
(Photo by Bernd) This is Sepia prashadi, the hooded cuttlefish. Cuttlefish hunt by visually stalking their prey and then shooting out their tentacles to grab it. Thus, they need to have a binocular field of vision so that they can accurately catch prey. This little guy's eyes are apparent on either side of his head (look for the curved, black pupil slits.) As you can see, cuttlefish can look in front of themselves with both eyes.
(Photo by Nick Hobgood) This is Sepia latimanus, the reef cuttlefish. Here you have a better view of the eye. The eyes are not closed - the pupil of cuttlefish is always a horizontal slit.
(Photo by Nick Hobgood) This is another S. latimanus, showing a different coloration.
(Photo by Nick Hobgood) This is Sepioteuthis lessoniana, the bigfin reef squid. Most squid normally have mostly monocular vision, but can move their eyes towards the front of their head to have temporary binocular vision.
Euprymna scolopes (Bobtail squid in orange form).(Photo by Nick Hobgood) This is Euprymna scolopes, the Hawaiin bobtail squid. In this photo, you can see the cuttlefish-like pupil shape and the existence of binocular overlap.
(Photo by Michael Vecchione) I'll leave you with the bizarre-looking eye of Helico pfefferi, the piglet squid. I don't know anything about them, but they sure look cool.
Thanks for reading!