Named after mathematician Carl Friedrich Gauss (rhymes with “grouse”), Gaussian (“gow-see-an”) blur is the application of a mathematical function to an image in order to blur it. “It’s like laying a translucent material like vellum on top of the image,” says photographer Kenton Waltz. “It softens everything out.” A type of low-pass filter, Gaussian blur smoothes uneven pixel values in an image by cutting out the extreme outliers.