imagemeister wrote:
Don't be afraid to put a Canon 500D lens on the front for close-up work !
Unfortunately, Canon doesn't make a 500D in 67mm diameter to fit the 70-200/4L lenses. Rather than go to a third party close-up diopter of unknown quality, you might want to use macro extension tubes... The Kenko or Opteka set are reasonably priced.
The 70-200mm f4L non-IS version is a superb lens. Very sharp, probably in large part thanks to the fluorite element it uses. It's about the least expensive lens you will find with a fluorite element. (Nikon only recently introduced a 70-200/2.8 with FL element... and charges $3000 for it... $1000 more than their non-fluorite version. The next "cheapest" Nikkor with fluorite costs over $10,000.)
If at all possible, I'd recommend the IS version of the Canon 70-200/4L. Yes, it costs more, but this lens is one you'll likely want to use handheld a lot.
Either way, the Tripod Mounting Ring A2 is a good, but separately sold accessory to have with the 70-200/4, but especially might be wanted with the non-IS version. The Canon OEM ring is rather expensive (around $150).... but there are third party "clones" that seem to work fine and cost about $50. If you shop for them and also find the even cheaper ($25 or less),
avoid those. Their plastic and prone to breaking.
If you buy used and it doesn't come with a lens hood, the ET-74 it uses is pretty easily found. The Canon OEM hood is rather pricey at about $40... but there are $12 clones, such as Vello that probably would work just fine. If you prefer a "tulip" style hood, like the Canon 70-200/2.8 lenses use, JJC makes both black and white versions of one (LH74T).
All the Canon 70-200mm lenses are very well built, sealed for weather resistance, with quite high performance USM auto focus. They're truly pro-grade "work horses".
It will work well with a quality 1.4X teleconverter, too... either Canon II or III would be very good... Less expensive Kenko Pro 300 and even more affordable MC-4 also are said to be quite good. I wouldn't try a 2X teleconverter... there's more loss of image quality and the combo of a 2X and an f4 lens won't be able to autofocus on a 7D. Still, could manually focus it, but that sort of defeats some of the high performance aspects of the lens.
No worries about buying used from B&H... They screen their used items carefully, but also give some right-of-return and warranty, in case anything goes wrong. B&H has gotten a lot of my money over the years... some of it for used items.