According to DZOptics, the most important factor in choosing a macro lens is its focal length, since this will determine how close you can get to the object to get the 1:1 magnification factor. There are macro lenses with focal lengths of 50, 60, 65, 100, 105, 150 and even 200 mm. Their differences are that the shorter focal length lenses also have a shorter focusing distance, while those with a longer focal length also have a longer focusing distance.