Aprendiendo Photoshop Illustrator Indesign

tolerance Adobe is really talking about luminance or how bright a pixel is. A tolerance of 20 means that when you click on a pixel with the 'sample size' set as 'point sample' then all contiguous pixels with a luminance of +20 through to -20 of the pixel you clicked on will be selected, with the luminance being calculated as the average luminance of the red, green and blue channel.