I got the Canon versions for the same reason as Neuro, for use with my 600mm, but from what I hear and read, the Kenko will work just as well. Giving the short DOF, I strongly recommend a macro focusing slider and the best I have found is the Really Right Stuff. It is very high quality, very smooth. For really close ups I use the Novoflex bellow. But then your mobility become quite snailish.