7 out of 10 points and recommendedcheap, light, longsoft and CA at wide apertures
I picked this lens up for its range. I use it on a T2i. I'm more of a wide-angle guy so I just wanted this lens for when the urge struck me to take pictures of birds and far away things. More and more I've become interested in telephoto work and have considered trying to pick up gigs that would require a telephoto zoom. I paid 75 dollars used from KEH, and I got the first generation, but I believe it's basically the same as the second and third and the USM in terms of image quality and build, for the most part.reviewed June 9th, 2011 (purchased for $75)
As others have already said, from 75-200mm the lens produces good images. Stopping down helps, but it never gets as sharp as say my 50mm f1.8.
From 200-300mm there is significant CA in high contrast situations, especially anytime you're photographing something white. When I first realized the terrible CA with this lens I was pretty disappointed. Stopping down helps but doesn't remove the CA.
*I wanted owners and potential owners of this lens to know that there is a homemade solution to the CA problem with this lens. I've found that if you manufacture a 58mm disk from black material and then make a 3/4 inch hole in the middle of it and place it on the front of the lens, this acts as a way of manually stopping down the lens to an equivalent of about f/10 (while it is really wide open at f5.6), and it totally removes the CA! I've also found it to improve sharpness. I'm talking primarily about 300mm here, but it can work at shorter lengths too. Obviously the wider the hole you have in your disk the larger the aperture and potentially more CA you'll have, and the smaller the hole the darker and more difficult it will be to take pictures of anything moving, so you have to find a median, and a 3/4inch hole works well I've found.
Here is a link to the a crop showing the purple fringing: http://www.flickr.com/photos/lukes_shots/5821111714/in/photostream/
And here is a link to a crop showing a shot with the homemade diaphragm: http://www.flickr.com/photos/lukes_shots/5820551691/in/photostream/
Aside from that, the AF is only good in good light, and even then it isn't perfect and it's loud and slow, but it can work pretty well if you set your center focus point only. Manual focus works well when you need critical focus.
The build quality is ok, but I've had better. I'll eventually probably invest in a 70-200mm 2.8 of some brand, hopefully canon but maybe tokina, to replace this guy, but if you're on a budget and can work around its limitations, it's not an unusable lens.
In fact, I've taken pictures of wildlife and cropped in on the photos and they still look pretty darn good. I also took pictures at a horse jumping event and compared them with a pro who uses a f2.8 biggy of some sort and mine looked just as good if not better...i set my color and contrast really high in-camera, making vivid photos and hers were all neutral and more average looking.
7 out of 10 points and recommendedsharp, light, compact, IS, cheap priceplastic mount, build quality, bad zoom and focus rings
This lens came with my T2i. I used it in Europe and Corsica and found the images to be good, but I also was using a 24-105 L at the same time and the images from it were always better, obviously. I also have owned the first generation 18-55mm without IS and could not really tell a difference in the quality, build-wise or optically.reviewed June 10th, 2011 (purchased for $150)
I thought this lens was good, but not good enough to keep. I sold it and ordered the Sigma 18-50mm f2.8-4.5 OS HSM, another entry-level midrange zoom. I wasn't able to do a direct comparison but I feel that the Sigma outperforms the canon in most areas, except CA and color balance. I've come to realize I use CPL and grad filters all the time and the sigma allows use of these with its non-rotating front element, and this makes a HUGE difference for me in terms of getting the pictures I like to take.
My copy of this canon lens also had a terrible zoom ring that was loose around 35mm and tight and difficult to adjust around 18mm and 55mm. The focus ring is a joke.
If you need a knock-around lens that delivers great photo quality, don't bother with other entry-level lenses from third-party makers, because this canon will deliver sharp, contrasty photos. But if you need advanced features and build quality along with equal photo quality, the Sigma 18-50mm f2.8-4.5 OS HSM is a better choice.