Why Do Dog Eyes Change Colors in Photographs?
Does your dog have a mood ring in his eyes?
Caroline Coile |
Posted: October 7, 2014, 8 a.m. PST
You take a picture of your dog with a flash, and what comes back but a photo of an obviously possessed ghoul, eyes shining yellow or orange or green or red. Is he possessed? Angry? Or just trying to ruin your photo op?
Photo from NewSchoolofPhotography
The dog's eyeshine is akin to the redeye that messes up so many pictures of people, but with some differences. Here's the science part of the explanation: If you shine a light into your dog’s eye, part of that light is actually absorbed by the visual photoreceptors (the retina's rods and cones), which send a nerve impulse in response and allow your dog to see. But part of the light manages to sneak past the photoreceptors, only to hit a reflective surface behind the retina, the tapetum lucidum. The tapetum is made up of thousands of tiny reflective cells. The dog doesn't have as many as the cat, which is why cat eyes reflect even more. Humans don't have a tapetum at all---we'll get to that.
The tapetum reflects the light back through the photoreceptors for a second chance at absorption, increasing his ability to see in the dark, but once again, some of the light sneaks past and now comes right back out the pupil. No, it’s not like your dog has beams of light shining from his eyeballs, so don’t get any ideas about throwing away your flashlights and just aiming Chihuahuas down a dark path. The only way you can see this light is to be lined up so as to be looking straight down into the dog’s pupils. This is what happens when you take a flash picture with your camera, and it’s why your dog’s eyes may glow.
Some people think the color indicates the dog’s emotional state, sort of like a built-in mood ring. But it doesn’t. The tapetum of individual dogs tends to be of different colors, and that’s why some dogs have green eyeshine in photos and others have yellow. And just because your dog may have redeye doesn’t mean he’s seeing red; he may be a dog without a tapetum, in which case the red comes from blood vessels at the rear of the eyeball---which is what causes redeye in humans.
Still, eyeshine can tell you a little about a dog's mood. If he's excited or scared his pupil will be wider, leading to more eyeshine even in brighter light. Just as with people, you can avoid it in photos by taking pictures without a flash, by taking them when the dog isn't looking straight at the camera, or to a lesser extent, by using the redeye prevention mode on the camera. But that eyeshine can come in handy when you're searching for your dog on a dark night, as he thinks he's carefully hidden in the backyard--except for those two bright beacons giving him away!
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