The image of the subject, which is taken by both lenses, will have same magnification, however the size of backgrounds will be different. The picture, which is taken by 50mm/f2.8 EX Macro Lens, will have wider background if compared with the 105/f2.8 Macro Lens. Further, lens to subject distance will be different for making life size pictures with both lenses. The subject to lens distance for 50mm/f2.8 is 40.5mm/1.7in., however this distance is 120mm/4.7in., for 105/2.8EX lens.