PSYB51H3 Chapter 3-5: CHAPTER 3-5
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Contrast: difference in luminance between an object and the back ground, or between lighter and darker parts of the same object. Acuity: the smallest spatial detail that can be resolved. 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. To calculate visual angle of your resolution acuity divide size of the cycle by the viewing distance at which you could just barely make out the orientation of the gratings, then take the arctangent of this ratio. This (cid:396)esolutio(cid:374) a(cid:272)uit(cid:455) (cid:396)ep(cid:396)ese(cid:374)ts o(cid:374)e of the fu(cid:374)da(cid:373)e(cid:374)tal li(cid:373)its of spatial (cid:448)isio(cid:374): it"s the fi(cid:374)est high-contrast detail that can be resolved. The limit is determined by the spacing of photoreceptors in the retina. Sine wave grating: a grating with a sinusoidal luminance profile. Light intensity in such gratings varies smoothly and continuously across each cycle. Aliasing: misperception of a grating due to undersampling.
