Triangles, as all elements in this section of the book, are used to bring the subject of the image to its centre. Not physically but to make them the important element. So to use shapes, lines, depth of field and focal lengths can make an image more powerful, it can direct the viewers attention or play with it. To make triangles and other shapes we must remove distractions that break these forms. This removes distractions from the picture as a whole. Like all other techniques here, they are tools that can be used to impose order on the world at large allowing us to almost extract the form of image from the world around us. They are reductions. Order.