I'm not a pro, and a pro has different needs. I've been corresponding with Sue about my Sigma 170-500mm f6.3, that I purchased for occasional wildlife (wild-living?). I don't like it; optics do not seem the best, and even on a sturdy tripod (using self timer) there seems to be enough shake to blur the image. [I can't whine about the lens for shaking, that seems inherent in a long lens. Guess I have to carry some sandbags. But maybe if it was faster the exposures could be shortened...] It is very heavy, and takes up most of the room in the camera bag. Has anyone used the lightweight catadioptric (mirror) lenses in the 500mm range? (It is a very long story) but I tend to always see things from a somewhat telephoto perspective. My work-horse is a Sigma 180mm f5.6 macro (focuses to 0.55m). So, Sigma CAN make good lenses. Will sometimes use a 35-70mm f4.5 zoom. By modern standards all three of these are pathetically slow, but suite my needs. The 35-70mm is neither wide enough, or long enough, but is cheap. Guessing from your work Rork, you want profssional equipment, and will be dissatisfied with too many compromises. It would seem you almost have to treat it like a business, and evaluate your return on investment. I know it is difficult to set lust aside, but will the new lens pay for itself? It seems you have already evaluated your work habits pretty thoroughly.