• how the eyes see color

How Does the Eye See Color?

The won­der­ful pre­ci­sion instru­ment that is the human eye can do some pret­ty remark­able things in coor­di­na­tion with the brain. Adapt­ing to see in the dark, being able to process depth per­cep­tion and the abil­i­ty to dis­tin­guish even the slight­est vari­a­tions of col­or are some the very things that the eye and brain can do. The way our eye sees and process­es col­or is con­cep­tu­al­ly sim­ple but very impor­tant.

 

The brain and eyes are con­nect­ed by the optic nerve, which trans­ports the images of the world we see to the brain for pro­cess­ing. In the eye, there are two dif­fer­ent types of pho­tore­cep­tors- rods and cones. The job of the rods are to allow some capa­bil­i­ties of see­ing in dim light con­di­tions or at night, the cones, on the oth­er hand, are used in bright light con­di­tions and to see col­or. We as humans have three types of cones for short, medi­um, and long wave­length light. So when light enters the eye through the pupil and pass­es through the lens it becomes focused on the back of the eye­ball where the rods and cones are. The light that enters the eye is of spe­cif­ic wave­lengths, which is what deter­mines the col­or of the object that we can see. The vis­i­ble light spec­trum for the human eye is from about 390nm to 700nm, just beyond the spec­trum lies ultra­vi­o­let light which is too short of a wave­length and infrared with is too large of a wave­length to process. The object itself actu­al­ly deter­mines which wave­length is reflect­ed back to our eye.

 

When we look at an orange, all wave­lengths of the vis­i­ble spec­trum are absorbed by the mate­r­i­al except for the spe­cif­ic wave­lengths that we process as orange, which are reflect­ed back to our eyes. To sim­pli­fy how it depends upon arrange­ment of elec­trons in the atoms of the mate­r­i­al is that when light, which car­ries ener­gy, strikes an object and some of it is absorbed and some is not depends upon the elec­tron struc­ture of the mate­r­i­al. We see an orange as orange because the elec­trons in the atoms of the orange peel absorb all oth­er wave­lengths of the vis­i­ble light except orange, which are reflect­ed back to the eye. Once the orange wave­lengths reach the eye, the cones that cor­re­spond to that wave­length are then stim­u­lat­ed to a cer­tain degree and then that infor­ma­tion is passed to the optic nerve to the brain to be processed by the visu­al cor­tex into the “col­or” orange that we per­ceive.

 

While we are much bet­ter at dis­tin­guish­ing vary­ing col­ors and degrees of col­or than most mam­mals, some crea­tures have four types of cones that allow them to see parts of the light spec­trum we are unable to. Some insects, birds and fish have been found to see some degrees of ultra­vi­o­let light, which have too short of wave­lengths for us to see.

 

How many col­ors can the human eye see? Despite not being at the top of the evo­lu­tion­ary vision chain, humans are still able to see and process quite a range of col­or.  

January 18th, 2016|Comments Off on How Does the Eye See Color?

About the Author:

Born in Connecticut and raised in Upstate New York , Dr. Stetson graduated Cum Laude from Colgate University in New York, and then earned an MD degree with honors at the University of Vermont College of Medicine. He distinguished himself again in residency at the Albany Medical Center, where he obtained the highest percentile in the Ophthalmology Knowledge Assessment Examinations. Dr. Stetson has performed more than 50,000 refractive surgeries and has been on staff at Diamond Vision since 2004, before becoming Medical Director in 2006.

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