Sigma 17-70mm f/2.8-4.5 DC IF Macro Lens ...- User Rating: 
Summary for Sigma 17-70mm f/2.8-4.5 DC IF Macro Lens ...- Great all-around lens - sharp and light
Notes on Sigma 17-70mm f/2.8-4.5 DC IF Macro Lens ...- I bought this lens as a backup for my 24-70 f2.8 L. Now this is a lens I keep on most of the time, mostly because it's much lighter than 24-70L. I saw some reviewers complaining about it being soft at extremes. My copy is tack sharp wide open, including 17mm and 70mm. I was not able to find a setting on which this lens produces soft images. I use it on Canon 20D.
Autofocus is fast, and while not as quiet as Canon USM lenses, it's not noisy. The front element does not rotate, so using a polarizer is not an issue. You can't use manual focus ring when lens is set to AF (as possible on Canon L lenses), but most people never do anyway.
The lens is 2.8 at the wide end, which matches 24-70 (and so does image quality). At the long end it's 4.5, so you do lose an f-stop or so, but this lens is half the weight and third the price of 24-70. Plus it has additional range 17-24, which is quite needed on 1.6x bodies.
The built is quite solid. It does have some zoom creep though - set it to 70mm and point upwards, and it will slide back to 30mm or so. This is not a big deal (unless if you shoot with one hand), but it does not happen on L lenses.
Overall, I highly recommend it - get your own, you won't be sorry.
Sigma 17-70mm f/2.8-4.5 DC IF Macro Lens ...- User Rating: 
Summary for Sigma 17-70mm f/2.8-4.5 DC IF Macro Lens ...- Nice lens - if you can get a good one.
Notes on Sigma 17-70mm f/2.8-4.5 DC IF Macro Lens ...- I went through two of this lens to get a good one. The zoom range is perfect for a walk-around lens. Would be nice if the tele end is a bit longer, but then image quality would be compromised. Build quality is very good - feels solid and heavy. Zoom ring rotates smoothly. It produces colors so accurate that I almost don't have to adjust color tones in post processing. Sometimes it can misfocus for no reason. I'm not crazy about the 'velvet' finish on Sigma lenses and prefer a 'traditional' black finish, but it looks ok and keeps surfaces clean. 72mm front end (along with the included petal lens hood) may look a bit intimidating for the small size of the lens. In general, good job by Sigma.
Sigma 17-70mm f/2.8-4.5 DC IF Macro Lens ...- User Rating: Summary for Sigma 17-70mm f/2.8-4.5 DC IF Macro Lens ...- Great all around lens
Notes on Sigma 17-70mm f/2.8-4.5 DC IF Macro Lens ...- I have found this to be a great all around lens. The pros of this lens are that it does a really great job focusing and has very sharp pictures in most situations. It is very fast. I have captured bees in flight and have been amazed with the clarity. The color is spot on. I am used to having to adjust the color/saturation in photoshop after uploading photos. I rarely have to do so with this lens. I also love that you can get very close to the subject and still focus. Makes macro type work very enjoyable. This isn't a true macro lens but it does a very nice job as "almost macro".
The cons are: this is a heavy lens. I would not want to carry this around my neck all day long. That is a pretty minor con..definitely wouldn't deter from buying. It also does poor in low light. I had to shoot a wedding after sunset and this lens was very soft (focus) in such conditions.
It can be soft (focus) at the end (70mm) also.
I would highly recommend this lens if you want to replace the kit and have a great lens that rarely leaves the camera.
Sigma 17-70mm f/2.8-4.5 DC IF Macro Lens ...- User Rating: Summary for Sigma 17-70mm f/2.8-4.5 DC IF Macro Lens ...- Great "Walkaround" Lens at a great price!
Notes on Sigma 17-70mm f/2.8-4.5 DC IF Macro Lens ...- I was looking for a good every day lens that I could take with me on a trip to San Francisco this past summer but being just a light hobbyist, I didn't want to spend the money for the high cost of some of the canon lenses like the 17-40L or the 17-55IS. So after reading alot of the helpful reviews here, I decided I would give this lens a shot and I'm very happy that I did.
The image quality on this lens is far better than the kit lens that came with my Canon XTI 400D. It actually feels like a whole different camera now. Pictures are sharp and the contrast and color the lens produces are head and shoulders above the kit lens. Also the extra reach this lens has over the kit lens comes in handy too.
At 17mm, the f/2.8 really works well indoors in lowlight situations, but it does stop down quickly...at 20mm, it already jumps to f3.5 and quickly goes up from there. The lens focuses fast and not as loud as I'd expected(going off of some other reviews) and the build quality is good also.
Some extra bonuses that I was happy about...
The Macro feature is a definite bonus, I can zoom into an object that's right up against the lens and it'll still focus well. The lens even came with a hood as opposed to having to buy a separate lens hood($45)for a canon lens.
A few things that were on the negative side...
The lens does tend to hunt in very low-light situations and there is some barrel distortion when shooting wide. Also it's much larger than the kit lens but you do get ALOT more lens so the trade off in weight is well worth it. Plus, I have a battery grip on my XTI which nicely balances it out.
Overall, the pros for this lens far outweigh any cons that this lens might have. It's nearly half the cost of the 17-40L f/4, and almost a third of the cost of the 17-55IS f/2.8. For someone that mainly shoots as a fun hobby on weekends, this was the perfect lens to fit my needs.
Sigma 17-70mm f/2.8-4.5 DC IF Macro Lens ...- User Rating: Summary for Sigma 17-70mm f/2.8-4.5 DC IF Macro Lens ...- Great addition to my collection
Notes on Sigma 17-70mm f/2.8-4.5 DC IF Macro Lens ...- I am a photographer on a budget, not a pro, not a novice, I fall somewhere in between. Maybe it's an obsession for me, an expensive hobby to be sure therefore I like to save money where I can, when I can. This lens aligned well with my collection, I have an 18-55mm (kit), 28-135mm (kit), 50mm f/1.8, 100mm f/2.8, and 70-300mm f/4-5.6. I bought this because the 18-55 just isn't up to par. The 28-135 is much better than the 18-55 but doesn't have the wide angle. This lens for $375 fills that wide angle and fills the gap to my 70-300mm perfectly. Overall I'm very impressed with this lens; I just spent a week in NYC taking photos and used this lens almost exclusively. I am very impressed the with the quality, is it L quality, no, did I pay for L quality, no.
By the way, I now have an 18-55mm and a 28-135mm for sale now if anyone is looking for one.
