When I bought my 40D I shot without a lens hood on my 17-85 kit lens. I bought a lens hood after shooting without one for a month or two. I always put a lens hood on my lenses because I don't want a shot ruined by flair.
Zeidora, there is a lens hood specifically designed for the MP-E 65, but it is very odd-looking. The hood is very short, and the walls taper inward markedly. Most people go to great lengths to diffuse their light source, so I don't imagine that directional flare is much of a problem in real life.
Hi Nancy (again)! thank for that pointer. I had not been aware of that hood, but will get it. I fully agree on diffused light. Have lately been twisting the MT24EX heads mounted on Wimberley plamps away from the subject onto white card board. Works quite well. The purpose of the hood is not only for direct flare, but for better overall contrast and color with fully diffused light.
Usually I carry body, nine primes mostly with filters and hood, two flashes, diffusors/reflectors, tripod, pol, NDs, water, food. It's about 40 lb. LF with about 6 lenses (one triple convertible) starts at 50 lb without water. Usually don't walk more than 5 miles in a day; I'm slow.
And, yes, I do work out.
Not all lenses. The 17-40L lens hood is all but useless. I've decided to simply leave it behind. Also my EF M 22mm lens has no lens hood but it does have a clear protector filter on it permanently. I also don't have hoods for my FD lenses.