My brother-in-law is a managing partner at a green house - I have not taken advantage of this fact enough. Yesterday morning I went in an hour before the store opened, and spent some time shooting. I set a custom white balance on my Canon 20D and, using an adaptor, I mounted an old Nikon M extension tube (27.5mm extension) and then put on a Nikkor 135mm f/3.5 (AI mount). I found this combination pretty good for getting a half decent magnification while providing some working distance. On my first trip out, I chose to use the M extension tube with my Micro Nikkor 55mm f/3.5 (Non-AI), for life size magnification. Unfortunately the tripod to table display distance was too great for me to get close enough. A little research shows me this:
Total extension used / Focal length used = Magnification
for my setup this was...
27.5mm / 135mm = ~ 1/5
However the 135mm lens does extend about 10mm when focused to its closest setting, so the maximum magnification may be up to ~1/4
While 1/4 life size is not great for 'Macro' work, I do get a lot of working room, and fairly close up. Compare this to the Canon EF 85mm f/1.8 which has a max magnification of 0.13x (or about 1/8th)
Here are the photos!
