It's so handy for bee shots that I have only recently started to use the 40-150 Pro instead, sometimes. The 12-40 focuses to higher magnification without tubes. I've never tried extension tubes because the lens front element gets pretty close to the subject as is. I sometimes have a problem with the lens casting a shadow in the frame at closest focus, so awareness of your light sources becomes important. It's very sharp, even at the 'unsharp' 40mm end of the zoom range.