The Visible Spectrum And how we see it

What is Visible Light? • The cones in the eye are only sensitive to a narrow range of EM frequencies. • Visible Light – that which can be detected by the eye

Red Light 780 nm – 620 nm Orange Light 620 nm – 597 nm Yellow Light 597 nm – 577 nm Green Light 577 nm – 492 nm Blue Light 492 nm – 455 nm Violet Light 455 – 390 nm

Cones are the color-sensing cells of the retina. • When light of a given wavelength enters the eye and strikes the cones of the retina, a chemical reaction is activated resulting in an electrical impulse being sent along nerves to the brain.

Cones and Color • The eye consists of three cones – Red Cones – Green Cones – Blue Cones • Each cone is sensitive to a different range of frequencies of the visible spectrum

The red cone is not only activated by wavelengths of red light, but also by wavelengths of orange light, yellow light and even green light. The green cone is most sensitive to wavelengths of light associated with the color green. Yet the green cone can also be activated by wavelengths of light associated with the colors yellow and blue

Color by Reflection (Subtractive) Certain wavelengths can be subtracted from the full spectrum (by being absorbed by a substance) leaving the other wavelengths to pass into our eyes All colors are absorbed except yellow White light – containing all colors of the spectrum hits an object only the yellow light waves are reflected off the object and hit the eye *Most common way we see color*

Why do printers use Cyan, Magenta and Yellow? • A dot of G would subtract B and R (two colors) • Since Cyan is a combination of G and B, it will only subtract R (only one color) • This leaves more colors to reflect and mix together to form all the colors we see printed

Additive Color Involves light emitted directly from a source into our eyes. Combination of colors produces different colors Where you see this process: • Stage Lighting (projection lighting) • Computer Monitors • TV sets

White vs. Black • White Light – presence of all color frequencies in the spectrum • Black – Absence of all color frequencies in the spectrum