Aspect Ratio is the ratio of a picture's longer dimension to shorter dimension - or its length to width. 35mm film and most digital SLR's usually have an aspect ratio of 3:2 which can produce 6 in. x 4 in. photos. Aspect Ratio is particularly important when printing photos. If you try printing to a size that doesn't conform to the film's aspect ratio, then your photo will either get cropped or will have white space around the edges. Point and shoot cameras and computer monitors usually have an aspect ratio of 4:3.