Filling the four corners of the frame raises the compositional bar, asking one to not only isolate the subject (see previous news article), but to use the frame as efficiently and as powerfully as possible. On page 7 of The Art of Photographing Nature, the authors discuss the specific task of filling the four corners of the frame. Editor Martha Hill suggests that this is simply working within the space dictated by the rectangle of the viewfinder. A simple concept, but its not easy to do, especially when the subject is in motion.
The bottom line: good composition is a matter of awareness. Try as best you can to be conscious of your entire frame. Youre looking, of course, to fill the frame with content, but also with design and visual flow. Photographers who can do this juggling several important intellectual tasks at once and getting it right can be confounding to beginning photographe