I tested out the Tamron on my 7D and 7D2 cameras because I am going to the San Diego Safari Park Butterfly Preserve on Wednesday. Of course, the Canon macro is not going to arrive before then but, I have decided to use my 100-400mm f/4.5-5.6L IS II lens for the butterflies. I would guess that a CF card is somewhere near the size of a butterfly. I tried my 100-400mm with a 20mm extension tube (which is the only extension tube that I own) and came up with this shot.
It is pretty amazing, This is at 400mm hand held with IS on. 1/20 second, f/5.6, @ ISO 1600 ambient light at my computer desk. From about 36-inches from the subject. This is a full 1.6x crop image with no cropping in Photoshop...
I can shoot from closer using 100mm and 200mm and also pretty well fill the frame with the CF card.
Tomorrow, I will play with this flash rig for close-up photography using my 100-400 Mk-2 lens on the 7D2 camera...
Actually, shooting with 400mm will allow me to get close-ups of some creepy-crawlies that might be frightened away if I got closer with a camera/lens...
The really neat thing about the 100-400 Mk-2 is that if I have it with me when traveling, I can get "pretty close" without any addition of an extension tube and can really get close with the 20mm extension tube. The 20mm tube weighs less than nothing to carry on a trip...
My next experiment will be to add the 1.4x extender on with the extension tube and see what kind of image that I can get from that combination...