It seems that there are two different ways of depicting MTF charts for lenses ev en though this shouldn't be. Ernst Wildi explains in his book on the Hassablad c amera that the horizontal axis is image height with the leftmost border as the l ens center. The fourth spacing to the right is then 40 degrees off axis. More co nventionally, the horizontal axis shows the modulation frequency of the reproduc ed image. Why is there a difference between the two? I also wanted to know if Te ssars have better contrast than symmetrical lenses. Thanks in advance.