I say make sure you use a good macro tripod such as a Redged, the Canon dual Macro flash and a focusing rail like the Novoflex Castel-Q. Along with the 100 you'd have an amazing kit with a steady image. I've used mine with the Tamron SP 1.4 TC (same as the higher end Kenko) but the IQ def degrades. If used with the right tools, such as above) you have fantastic cropping ability if the image needs it. Well, ymmv but it works great for me on a 5D3.