BIO 208 Lecture Notes - Lecture 25: Point Spread Function, Visual Angle, Visual Acuity
19 Sep 2016
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25- visual acuity: why cats are legally blind. In ny, legal blindness is defined as a visual acuity of 20/200 or less in the better or stronger eye. Measuring visual acuity: this visual acuity test, the snellen eye chart, measures how well you can see the differences between lines and spaces that make up letters, normal vision is defined as 20/20. A person with 20/50 vision can see at 20 ft what a person with normal vision can see at 50 ft. Spread function psf): psf is a technical term for blur. Instead we see a uniform gray when looking at a series of stripes. Measuring visual acuity: visual angle: we measure the visual angle using degrees. 60 minutes: the number of degrees of visual angle that an object covers on the retina depends upon its distance from the eye. A quarter at arm"s length covers 2 degrees of visual angle.
