Question

Question 6 Describe Purkinje Phenomenon and Explain Purkinje Mechanism. Discuss the Importance of Purkinje Phenomenon to the Nature of Vision

Answer 1

Describe Purkinje Phenomenon.

Purkinje phenomenon is the tendency for the peak luminance sensitivity of the eye to shift toward the blue end of the color spectrum at low illumination levels as part of dark adaptation. In consequence, reds will appear darker relative to other colors as light levels decrease.This effect introduces a difference in color contrast under different levels of illumination.

For example, in bright sunlight, geranium flowers appear bright red against the dull green of their leaves, or adjacent blue flowers, but in the same scene viewed at dusk, the contrast is reversed, with the red petals appearing a dark red or black, and the leaves and blue petals appearing relatively bright.

Discuss the Importance of Purkinje Phenomenon to the Nature of Vision.

The Purkinje phenomenon is important in nature of vision and has a number of applications in various vision scenarios. The insensitivity of rods (present in eye) to long-wavelength light has led to the use of red lights under certain special circumstances – for example, in the control rooms of submarines, in research laboratories, aircraft, or during naked-eye astronomy.

Submarines are well lit to facilitate the vision of the crew members working there, but the control room must be lit differently to allow crew members to read instrument panels yet remain dark adjusted. By using red lights, or wearing red goggles, the cones can receive enough light to provide photopic vision (namely the high-acuity vision required for reading). The rods are not saturated by the bright red light because they are not sensitive to long-wavelength light, so the crew members remain dark adapted. Similarly, airplane cockpits use red lights so pilots can read their instruments and maps while maintaining night vision to see outside the aircraft.