Joggie, the 300mm. f/4 has become my favourite macro tool for insects because of the longer working distance. My original idea was to purchase the Micro 200mm. f/4 or the Sigma 180mm. f/3.5, but I opted for the versatility of the 300mm. By itself, the lens focuses to 43 inches working distance for a 1/3x magnification (no crop factor.) A 36mm tube will result in 1/2x and loss of 1 f/stop and 32 inch working distance. Alternatively, I have been using my TC17E teleconverter which yields 1/2x at 43 inches working distance but 1.5 stop penalty. However, without using extensions, the Canon 500D diopter will get me right to 1:1 with a 13 inch working distance. When I add the TC17, I can get 1.8x with quite good quality, but a heavy rig to hold for extended periods.
For lighting, I am using an SB800 mounted above the camera on a stroboframe flip bracket and angled downwards by means of a ball-head. I have also found it convenient to mount the flash directly to the tripod foot, which has been rotated to be on the top of the lens. It is also possible to use the SB-R200 rig, but I favour the higher output SB800 flash. (The Sunpak ring flash is too small to use on this lens - the results could be interesting.) To add to my repertoire, I have ordered a "Better Beamer" flash extender which should focus my flash to 300mm.
More specifically, with this subject, I used a 20mm. tube and the flash mounted on the tripod foot, and exposed manually. I doubt if any ambient light registered at f/22.
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