Most helpful positive review
610 of 648 people found the following review helpful
Good value - useful all-in-one lens
on August 9, 2005
Like a baseball player with a decent batting average, some power, a little bit of speed and fairly good fielding ability, the Tamron 18-200 lens won't be an All-Star any time soon because it does not excel at any one thing. But, like that $500k/year utility infielder, this lens DOES provide a very good all-around value for what it is. Does it compare to a prime lens at either end? Heck, no. Is it a good lens to use when you can't carry a wide choice of lenses with you? Absolutely.
I've been using this lens on my 20D quite a bit and have only a few minor gripes: it tends to hunt for AF (especially as you get closer to 200mm), and it's not the quietest lens I've used.
An earlier reviewer mentioned that it maxed out at about 160mm. My own analysis shows that it is short of 200mm, but not by that large an extent; I found it much closer to 190. Still, there's no doubt that these zoom lenses with extreme ranges like this have a built-in fudge factor.
Another reviewer described the problems he encountered when using two screw-on filters. There aren't too many primes that I've used that will avoid vignetting when using two filters. Heck, my 10-22 can barely handle one extra-slim. As for darkening the image - well, you're adding two more pieces of glass to a highly-complex lens assembly... just asking for trouble.
As for the concern regarding blur at longer focal lengths, I highly recommend the use of a tripod. I noticed the exact same thing - blur and lack of sharpness - at lengths over 100mm. Keep the old rule of thumb in mind - if you're shooting handheld, your shutter speed should be no slower than the inverse of your focal length. A 200mm lens on a 20D (or Rebel XT for that matter), is an effective 320mm - I wouldn't recommend shooting any slower than 1/500 at max zoom with this lens - UNLESS you're using a tripod. When I mounted it firmly, I got great shots with no blur.
Keep in mind that you get what you pay for here: the convenience of a wide-angle, normal, and moderate telephoto lens in one piece. If you're shooting professionally, or need absolutely perfect images, then carry the three or four lenses that this would otherwise replace in your bag. But if you want one easy-to-use, satisfactory lens, go for this one. It's a jack-of-all-trades, ace-of-none kinda deal.