The Red Eye Effect

Dad: Ready?

My mother and I: Yes!

Dad: 1, 2, 3, say "cheese!"

My mother and I: Cheese!

(Camera flash)

My mother and I: Did it come out?

Dad: Nope, your eyes are red!!!

Entire family: UGH!!

In case you are wondering, this is not an excerpt from my new movie. This is an issue which has happened millions of times to millions of people: the red eye effect. Before people were able to just click a button to remove red eye on their iPhones, this unwanted camera effect ruined many precious photos. How is this unwanted camera effect caused?

Before we dive in, I recommend checking out my previous post about the eye and how it works. Reading it will help you understand the concepts in this post.

The process in the eye which causes the red eye effect actually has to do with what is in your skin. What makes your aunt's brother's cousin's roommate darker than me? The answer is melanin. Melanin is similar to a pigment in plants known as chlorophyll, which gives leaves their green color. Chlorophyll absorbs all wavelengths of light except for green, which is reflected back. Melanin is a  similar pigment, except it applies for heterotrophs. Instead of reflecting green light, melanin absorbs all wavelengths of light except for brownish red light. Because of this, the more melanin you have, the darker skin color you are. 

(Absorption Spectrum for Chlorophyll Above)

(Absorption Spectrum of Melanin Above)

How does all this relate to the red eye effect? The retina, the part of the eye which receives the inverse image, contains many melanin pigments. Because the flash of a camera is white, all colors of light are shot into your eye. Melanin reflects the brownish red light and absorbs the rest of the light, resulting in the red eye effect.

So the next time you are thinking about throwing your camera out the window because of the reoccurring red eye effect, think twice, because the only think you should be throwing out the window is your own eye. 

For more information on melanin, chlorophyll, and other possible causes of the red eye effect, please visit the sources below.

Melanin: http://www.news-medical.net/health/Melanin-What-is-Melanin.aspx

Chlorophyll: http://www.chm.bris.ac.uk/motm/chlorophyll/chlorophyll_h.htm

http://en.wikipedia.org/wiki/Chlorophyll

Red Eye Causes: http://www.yalescientific.org/2011/05/what-causes-the-red-eye-effect/