Look at a lens in terms of will I use it? Is it sharp all the way across the field of view? Do colors appear on the edges of white objects especially near the edge of the frame? Lines WILL converge but will do so less with a larger lens. That alone is a good reason to buy a Canon 7D or something like that to put a EF 16-35 1:2.8 L ll onto and shoot video that way. THAT lens is made to eliminate converging lines.