Cinematography-Theory-And-Practice

Functions of the EyeThere are many theories to explain the phenomenon of color vision.The most easily understood is the three-component theory thatassumes three kinds of light-sensitive elements (cones) — each receptiveto one of the primary colors of light — an extreme spectrumred, an extreme spectrum violet, and an imaginary green. There areabout seven million cones in each eye. They are located primarilyin the central portion of the retina called the fovea, and are highlysensitive to color. People can resolve fine details with these coneslargely because each one is connected to its own nerve end. Musclescontrolling the eye always rotate the eyeball until the image of theobject of our interest falls on the fovea. Cone vision is known asphotopic or daytime vision.Other light receptors, called rods, are also present in the eye butthey are not involved in color vision. Rods serve to give a general,overall picture of the field of view, and are receptive only to thequantity of light waves entering the eye. Several rods are connectedto a single nerve end; thus, they cannot resolve fine detail. Rodsare sensitive to low levels of illumination and enable the eye to seeFigure 12.3. Color is a crucial componentof this frame from Days ofHeaven. The primary red/orangetones function not only as pure colorbut also have strong associationswith mood and time of day — bothof which are important in the storyof this film. The shooting scheduleof the film was built around timesof day when shots like this could becaptured.Figure 12.4. A wave is definedby wavelength (distance betweenpeaks) and amplitude (height of thewaves). Frequency is a measure ofhow many waves occur in a second,usually expressed as hertz (hz).color229