I have just bought a SIGMA 18-300 MM F3.5-6.3 C DC MACRO OS HSM lens to go on my (2x) Canon 50D bodies. I also have Sigma 17-35, 35-70 and 70-200 DG EX f2.8 lenses (and the 2X convertor for the 70-200). I'm very perplexed as I've been shooting some test shots, tripod/still life, to see how the new lens stands up against the 'proper kit' and in all the tests the new lens is much better! I'm just a casual amateur doing this for fun but am in the position of being able to afford some nice kit (and, TBH, I need all the help I can get). All my old full frame lenses are 15 years old or more, and all were bought used but I expected them to be better than the new 'all in one' zoom. Am I missing something or should I just sell all the 'posh kit' and just have the one body and lens? Would having the old lenses professionally cleaned be worthwhile, the 70-200 shows a little internal marking/dust/fungus (it's the hardest used and, probably, oldest of the lenses, shows a fair bit of wear and was bought from a semi pro sports photographer) but the others only have a little external dust/fingerprints visible on the front elements and are, otherwise, almost like new.