Tamron and Sigma produce many good lenses. Despite my many years SLR experience, their lenses' quality manufacturing control and technology aren't quite there yet. Canon places the SLR product into many categories, from cheap to very expensive. You must trade-off whether how serious the picture quality you really look for. Mostly Canon-L-series SLR lenses produce very good pictures, but the price lists are too extreme ! I've heard comments for Tamron and Sigma lenses when using with Canon DSLR which are :
1. some errors and imcompatibility
2. many lenses deformed and deteriorated in just a few years.
Just a precaution. By the way, don't get me wrong. Many good and nice pictures were taken by many Tamron and Sigma lenses. But, it's like an investment to me making a purchase of lense. So, choose wisely. Good luck.
I just ordered a canon digital rebel,my first slr. What would you recommend as a good all around first lens with a good zoom foremost on my mind. I have heard that sigma is a good quality and cheaper alternative to Canon. Thank's.

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