I remember my pythagorean theorem A^2+b^2=C^2 and thought you should be able to use that to figure out how "wide" your lens will see at a given distance from your subject. For example, the Sigma 10-20mm has a an angle of view of 102 degrees. I figure you should be able to split that in two to form two right triangles and figure out 1/2 the width of the view you get when you use the lens at 1 foot, 5 feet, 10 feet etc. However, without knowing two of the three variables in the equation how can you (or is it even possible to) figure out how wide your view from that lens is given you are x feet from the subject? Am I making sense? Just overthinking my new toy I guess.