Tamron Lenses are famous for their price and focal length. They provides general consumers with a versatile lens walk around lens. Compare to Canon or other brand name lenses (Nikon, Olympus, Sony etc), Tamron lens are not as good mechanically and image quality because Tamron optimized their production on the price and size.
Some notable Tamron lenses are 17-50mm f/2.8. If you need wide angle fast lens for shooting in low light or want to create a great depth of field this lens is for you. Compare to Canon 17-55mm or Nikon 17-55mm, this Lens is a lot cheaper. Canon lens is sold at $1000, Nikon’s at $1200. Canon lens has image stabilizer and fast auto focus motor and Nikon has better built quality and fast auto focus motor (AF-S) also. Both Canon and Nikon lens are sharper especially on the edge. Complete review comparison of Tamron 17-50mm vs Canon 17-55mm IS USM is discussed here
Perhaps one of the most popular lens Tamron will be 18-270mm VC (Vibration Compensation). This new announced lens in photokina 2008 trade show has a massive range of focal length with no competition. The size and weight of the lens is also very reasonable for travel. In addition with VC (image stabilization), this lens is very versatile for day to day use. For Canon and Nikon shooters whereas the cameras does not have built-in stabilization, this lens VC will be helpful especially in long zoom. The price factor is very interesting too. It is cheaper from Canon or Nikon 18-200mm lens ($600 compare to Canon’s $700 and Nikon $650).
If you have camera with built in body stabilization, Tamron 18-200mm is a bargain lens for you. It is only $275.
The other thing worth to notice is the new Tamron 70-200mm f/2.8 Macro lens. This lens is also $300 cheaper than Canon 70-200mm f/2.8 usm. I thas decent macro capability and sharpness but it lack of auto focus speed which is essential for sport photography.
For the macro lens, Tamron has an excellent 90mm f/2.8 lens. But because the price differences are not that wide, I will suggest you to get brand macro lens instead.
In conclussion, if you are not into fast action such as sport photography, then Tamron lens give you versatility and price that irresistible. But if you are very picky about image quality and do not mind about price and mechanical quality such as auto focus noise and speed, then Tamron lenses might not be for you.
Click on the table below to see the comparison between some Tamron and Canon lenses
BC = Built Quality IQ = Image Quality