ps: why would you ever reverse a macro lens? reversing for macro only makes sense for "normal" lenses, as far as i understand, to try to get around the disadvantages of the "1 to many" optical design of a regular lens (turning it into many to one, which somehow seems to work better for macro)? or am i wrong?
Reversing a K50/4 Macro will give you higher magnification, due to the deeply recessed front lens element. Reversing acts like an extension tube in this case and image quality is also improved when magnification is greater than 1.0x.