For quite sometime, i wanted to get a Zoom lens for my camera (i own a Canon 1000D EOS camera), though i already have Canon 18-55, which i got it along with my camera kit. I often end-up in place, where i wanted to zoom, to take a close picture of something/someone, but just because, my kit-lens was very basic lens, but sufficient one for taking indoor pics. So, Zoom lens got added to my shopping list and became the next-to-buy stuff.
The main advantage of the First one (canon lens) is that, its from the maker of the camera which i own, and also promises an awesome image quality, even at the far end of the zoom. Also, it has a very good auto-focusing speed even at full zoom (compared to other available zoom lenses in market now). Adding to it, it also has the Image Stabilization (IS) factor, which is so much necessary, when you handle this lens in your hand (when not using tripod). With all these advantages, it comes with the whooping price of $542 (US) or Rs. 36000 (India). Another important factor to be kept in mind is that, changing lenses. Whenever i need the zoom factor or otherwise, i have to switch lenses. And not all time the environment will be suitable enough to switch lenses and the moments might get missed also.
This comfortable issue is mainly addressed by the Second one (Tamron lens), that one lens, covers the entire range, from reasonable wide-angle, to, super zoom, upto 15x. no change in lens required. But, the drawbacks with this lens, when compared to that of Canon lens, are the image quality and slow Auto-focus (though its very quick, but not as quick as Canon lens) at the far end of the zoom. Though, this being the only* (as of now) zoom lens which covers this huge range, also with VC (Vibration Cancellation, similar to IS in Canon lens), the price $630 (US) or Rs. 31000* (India) (*depends on where you get it. Since this lens is very very new here, in India, i got it for such a cheap price, without warranty though, but good box piece).
So, when it was a choice to make on, standard & quality Vs comfortable & affordable, i, this time, chose the second one, Tamron Lens. Yes, finally got the Tamron Zoom lens last week. And till now, i'm glad about that choice. caz, with the same amount, which i would have spent in canon lens, i could get a Tamron lens, tripod, another original Canon Battery and camera screen guard. thus, my camera got little heavy, but my purse got very light now (and always its that case, so np). And already Tamron lens, proved its purpose, when i tried this in my Trekking Trip.
Canon 1000D / Rebel XS with Tamron AF 18-270mm f/3.5-6.3 Di II VC LD Aspherical (IF) Macro lens