Monday, July 15, 2013

Class Starts Today: Apples to Illustrate the Purkinje Shift

Rods are relatively more sensitive than cones to blue and green light (shorter wave length). In addition, only about 1% of our cones are blue sensitive so the cones are relatively insensitive to blue.Therefore, in dim light, blues look relatively lighter and reds relatively darker than they do in the daylight.  This is the Purkinje Shift.

This painting of red apples in a blue bowl was painted to illustrate the Purkinje Shift. In daylight, the red cherries appear to be lighter or about the same value as their blue bowl. However, when it becomes dark enough to not see colors, turn the lights off, and wait 10 minutes to dark adapt. If you are fully dark-adapted, you will use just your rods and will not distinguish colors and in a few minutes, the blue bowl will appear LIGHTER than the cherries.
In today's class, we also made a red tomato white, black and super red by altering the color light shining on it.

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