PSY280H1 Chapter Notes - Chapter 3: Herman Snellen, Visual Acuity, Sine Wave

• School: UTSG
• Department: Psychology
• Course: PSY280H1
• Professor: Michael Mack

Document Summary

The eyeball functions essentially as a biological camera, but it"s not the same as one. Now we learn the path of image processing from the eyeball to the brain. Neurons in the cerebral cortex prefer lines, edges and stripes. Acuity is the smallest spatial detail that can be resolved at 100% contrast. Eye doctors specify acuity in terms like 20/20, but visual scientists use the smallest visual angle of a cycle of the grating that we can perceive. A cycle is one repetition of a black and white stripe. The visual angle of our resolution acuity = arctan (size of the cycle/ the viewing distance at which we can barely make out the orientation). The limit is determined by the spacing of photoreceptors in the retina. For example, with a sine wave grating, if the receptors are spaced such that the whitest and blackest parts of the grating fall on separate cones- we see the grating.