PSYB51H3 Chapter Notes - Chapter 3: Visual Search, Neural Development, David H. Hubel
Document Summary
Contrast: the difference i9n luminance between an object and the background, or between light and dark parts of the same object. Acuity: the smallest spatial detail that can be resolved at 100% contrast. Cycle: for a grating, a pair consisting of one dark bar and one bright bar. Visual angle: the angle subtended by an object at the retina. Eye doctors specify acuity in terms of 20/20, but vision scientists prefer to talk about the smallest visual angle of a cycle by the grating we can perceive. Under ideal conditions, humans with very good vision can resolve gratings when one cycle subtends an angle of approximately 1 minute of arc, or 0. 017 degrees. Sine wave gratings: a grating with a sinusoidal luminance profile. The light intensity in such gratings varies smoothly and continuously across each cycle. However, the visual system samples the grating discretely through the array of receptors at the back of the retina.
