Better than my EF-S 17-55mm f/2
924807
The lens is everything is cracked up (no pun) to be. Better than my EF-S 17-55mm f/2.8. I'm sure it will be even better on my soon-to-be new Canon 5D MKiii.
2054879
I recently purchased this lens as an upgrade from my Canon EF 75-300 III. I wondered if the image stabilization (VC) and advanced autofocus (USD) would make a big difference and the answer is a resounding yes. Here are some pros and cons of this lens:

Pros:
  Autofocus is super accurate. I always used my 75-300 in manual because the autofocus missed so often. This never leaves auto.
  Full-time manual - I cannot emphasize enough how important this is to me. If you don't know what full-time manual means, it is when you can manually adjust the focus ring while holding down the shutter for autofocus. Instead of having to switch to manual focus when you can't get the shot, you can fine tune it yourself. A perfect example of when you might need this is if you are shooting a bird in a tree. The leaves and branches may distract the autofocus, but you can make corrections without having to flip a switch. That can make the difference between getting the shot and missing an opportunity. There is no comparable lens in this price range with this feature.
  Solid construction - This is a heavy lens. It feels well-built without being too big to carry.
  Image stabilization - I have not yet found a situation where I need a tripod (although I haven't done any moon photography with this lens yet).
  Lens hood included - Canon tries to sell you a lens hood for $30 or more. This comes with the hood. It can be attached backward for easier storage.
  Zoom lock - Not that you should be pulling your camera out of the bag by the lens, but if you do, you can store it with the zoom locked at 17mm so you are not putting additional strain on the lens.

Cons:
  Size and weight - If you are not used to professional lenses, this will be the largest and heaviest lens in your bag. Not an issue for me - just a warning in case you've never used a pro lens.
  Slow aperture - At f/4.0-5.6, I'm stretching it by calling this a professional lens. Real professional lenses will be f/4 throughout the zoom range or even f/2. Fortunately, the image stabilizer allows you to leave the shutter open slightly longer without needing the tripod, so this isn't an issue most of the time. Just don't expect this to be great for indoor sporting events.
  Odd filter size - I think Tamron is the only company that uses size 62mm filters, so you probably don't have any laying around in your camera bag.

You can use this on either a full-frame or crop sensor Canon DSLR. I'm using it on a crop sensor (SL1) and it gets me really close to the action. I'll try to update this with some pics when I have more time.

Update: I added a couple of pictures. These were taken at the full 300mm and are uncropped so you can get an idea of the maximum zoom and image clarity. Also, I did not use a tripod for either picture. It was a very cloudy day when I took both pictures so that will help you see how it performs when light is lacking.
2560821
Many good and bad things have been said about this lens already, so I'll provide a narrative instead about my experiences with the 35L and 50 f/1.4.

I wanted to improve my composition as a budding photographer, so I borrowed a 35L to use on my T3i crop for a week. I was quite impressed by its build quality and AF! The contrast, bokeh and IQ were excellent from f/2 upwards. Even at f/1.4 - f/2, the 35L on a 1.6x crop was acceptable for casual portraiture. I knew that the 35L was very versatile on a full frame body, so I bought a Canon 6D after a couple of months. At the time of the 6D purchase, I felt like the 35L was "not worth the price" and it was "too old of a lens" so I went ahead to try out the 50mm hoping that it would be "just as good" as the 35L.

Wrong thought process!

I'll admit, the 50mm certainly has good contrast and IQ from f/2 onwards. However, its build quality, bokeh and AF were certainly not on par with the 35L. Plus its IQ below f/2 was lackluster (hence 4 stars).

What about the 50L? It felt great in store, but I already had a great experience with 35L on my 1.6x crop. Plus, my ambition was to shoot occasional night shots, group pictures, casual landscape, environmental portraiture and lifestyle in the near future - which the 35L excels at. I wasn't planning to shoot much at 80mm cropped much; I already had a 55-250mm EF-S on the T3i that covers the range for now.

Although the 50mm is a spectacular lens, I bought the 35L in the end.

There are two morals from this story for those who are on the fence between lens X and lens Y:

Moral 1: If you're invested into photography, don't be afraid to shell money out for great lenses. They will last you a lifetime!
Moral 2: Think hard about what you want to shoot in your journey - you'll be much happier in the end.
3327843
14-45mm is hands down superior to the kit 14-42mm in construction and smooth function. My 14-42 has a stiff/sticky, cheap feeling zoom action. The 14-45mm does not leave the kit lens impression (which it used to be) at all, and is clearly of superior design and execution.  A recent trip with the 14-42 on a GX1 body, on some pretty cold days, was a bit frustrating.  Handling the camera and using the stiff zoom ring was awkward.  Even on a tripod, it was a 2 handed operation.

Optically, things are much closer.  At 12 elements in 9 groups vs 9 elements in 8 groups, you would expect superior performance from the 14-45, which I do believe it delivers in some key areas for me. Both have 7 aperture blades, but I see smoother bokeh (out of focus areas) with the 14-45mm, than with the 14-42mm.  But this, like the other optical characteristics mentioned, range from subtle to just noticeable (save for distortion and edge/corner sharpness at some settings).  That speaks pretty highly of the optics quality of the 14-42mm. Both are about equally very sharp in the center, and I'd say from looking at my images, it would be pretty hard to tell the 2 apart.  The 14-45 wins in edge sharpness, noticeably so at some lens openings.  There is some vignetting evident with both when around 14mm, but stopping down to the sharpest lens openings (5.6-8) on each helped this very much.  I think the 14-45 handles and controls flare and contrast much better, but that isn't to say the 14-42 is bad.  The biggest optical advantage I can see with the 14-45mm is the low level of distortion it produces.  I was quite surprised by this.  The 14-42 isn't terrible here either, but at each end of the zoom range, the distortion has a very strange look to it (almost like a weirdly shaped pincushion) and I had a few images that were very difficult to correct.

I feel the 14-45mm is worth the extra money if you can find a new one; even a clean used one is worth it.  If you're just entering the M43 world, foregoing a body/lens kit and buying the pieces separately would be required.  14-45mm is slightly larger size, but I don't find this to be an issue, and again, the smoothness of operation makes holding and using these small bodies a much more pleasant experience.
1026840
I've been using the 70-200 f/4 for a couple of years, and realized that I really needed a faster lens with image stabilization. Justifying the price for a lens to feed my hobby was difficult, but am I glad I did!  First, this lens is larger (I had to purchase a new sling camera bag to fit the lens) and a lot heavier. I shoot a lot of action stuff, mostly ski racing, shot on the hill. This means that I can't put the camera down, or use a tripod or monopod - so the weight really puts a strain on the wrist during a few hours of shooting. But, there is no camera shake in my images. They are as crisp as is I shot from a tripod - just see the samples I uploaded.

Another big plus - I have the 2x adaptor from Canon. It was not really practical with my previous lens - slowed it down too much, required a tripod, too dark. With this lens - holy cow! Hand held shooting with a 400mm! See the samples - great quality and color.

I can't say enough good things about this lens. There are two different IS modes. Mode 1 is full stabilization. Mode 2 if for panning, say when you're following a moving skier or car.  It stabilizes the vertical but leaves the horizontal alone.  Typically an IS lens is pretty useless for action photos when you're panning the subject - Mode 2 saves the day!

The downside: The weight.  The image stabilization is loud - at first I thought the auto-focus motors were messed up.
700225
I recently tested this lens out during some light sports activities event in the park. I wanted something small and light but fast and tele. On my 7D it gave a good focal length, equivalent of about 135mm on a full frame. That was actually a bit too long and I had to back up a bit but no big issue. I wanted to freeze the action and so was using f/2 - 2.8 mostly. I already know f/1.8 isn't great so I avoided it. Here's how I got on -

The lens focused really fast, no issues there. In fact its fast enough that I could use one shot AF and shoot before the subject moved a significant distance. Truly impressive.

Bokeh was lovely too. The distracting background just melted away. Loved it.

At f/2 the dof is super shallow, just a few cm in most cases. I had a lot of blurry shots and out of focus shots. Chalk that down to user error. I shoulda used f/3.5 or more for the close ups.

But I wanted to really push this lens at the wide end so I just kept it there. I had enough decent shots thanks to the 7Ds AF so I wasn't too bothered.

Now, it wasn't until I looked at the images on my laptop that I noticed a lot of purple fringing. Visible even without zooming 100%! There was also some green and red CA too. Now, I know I can fix this BUT I don't want to HAVE TO fix it. even 20 pics that need correcting is time consumig let alone 200! Not ideal if you're a heavy shooter.

Skin on bright background was the worst culprit next to metal and reflective sharp lines. No other lens I have used gives this much purple fringing. It's ridiculous!

That said, as a f/2.8 prime lens for portraits it is a phenomenal lens for the price.  But as a f1.8 its not that great. Seems like a waste. Though it is very sharp and the color reproduction is good too. Maybe not as good as the 50mm f/1.8 II which is freakishly good for a cheap lens!

There aren't many other options for an alternative. I think there is a Zeiss but it's MF only. So that leaves the very expensive L option.

If I was a pro and did a lot of stuff at wide apertures maybe I'd get the L instead. As it is I don't make money from photography so a bit of purple fringing for cheapness sake is acceptable, for now. I will use this lens to practice my technique more. When I feel it is no longer meeting my needs I'll think about the L!
2232735
I upgraded from a Panasonic GX-1. The improvement for lowlight is quite good. The EVF is a lot better but it is taking time to get used to the new Menu. I miss the integrated flash, however the low light performance helps me push the boundary a bit.

When I paired it with the PRO lens and the performance went up a notch. Overall I do see other improvements in color and sharpness.
1474214
I've had this lens for a couple of weeks now, shooting with it on an E-420. My primary concern before buying were reviews citing slower and wandering AF as light becomes low. These are generally true, but it should be said that the only conditions I've encountered trouble with so far are indoors and at night, which is not a major knock against this lens. The AF is a little noisy but not intrusively so, and while the external focus tube precludes the use of a polarizer because it rotates during focusing, I understand the need for this kind of design in this price range. Optics are good enough that a sensor like the E-420's can't faithfully capture visible flaws in image quality. Capable of surprisingly delicious bokeh. Build quality is just fine and zoom action is smooth, AF/MF switch is nice. If you're on your first DSLR and need a first telephoto with a lot of focal length range, this is your top choice in the 4/3 system.
4762922
Simply put the image clarity you get with this lens is amazing. When you factor in that this glass is 50% of the cost of what you need to spend for a similar canon lens (which is NOT an L lens). The Canon 17-55mm sells for over $1k. The L glass 16-35mm sells for $1500. This glass compares to the L glass I own - I own the 24-70mm L and the 70-200mm f2.8 IS L (which is the BEST glass I have ever seen).

The brightness - the ability to shoot in low light and this is a tiny lens compared to my L glass and light. Not light as in cheap - but light as in not heavy like the 24-70mm L. it shoots very sharp - not as sharp as my 70-200 - NOTHING is as good as that. The range is very useful - great for shooting people - works super indoors. I bought and returned a 50mm f1.4 canon prime because I felt this lens performed better than the 50mm prime with the zoom set to 50mm.

IF you wish to buy a first upgraded lens for your camera and you can not afford a 70-200mm f2.8 IS L then buy this lens.
1265252
There's a newer EF 16-35mm f/4.0L with IS ; I would either buy the f/4 version or just get a wide angle prime. don't get me wrong, the 16-35mm f/2.8L is perfectly good, but unless you use it to take real estate shots all the time it may not justify paying or owning this lens... I found myself using my 24mm prime more often than this 16-35mm.
3233382
I stumbled on Breakthrough Filters accidentally when I was upgrading my lens kit for my Nikons. I recently added the Milvus 15mm/2.8, Otus 28mm/f2.8, and Otus 55mm/f1.4. The first two require 95mm filters, the last 77mm. A reviewer over at B+H mentioned these as an alternative to Heliopan, not because they cost less, but because they were better. I think that person is right. The machining and construction are superb, and I can find no fault in the glass. The slim 95mm UV does not vignette on the 15mm Milvus, but the X4 CPL does show some very modest vignetting. I need to do some additional test shots to compare to my Zeiss CPL & UV, but right now, were I buying my first filters for these lenses, I would be buying the Breakthrough, not the Zeiss.
3016917
At about $600, this lens might seem expensive for an F/4 (At about 24mm, it's F/4.5; F/5.0 around 35mm; F/5.6 around 50mm+). However, the image stabilization is excellent and fun to play with. It is easy to get very crisp images, even in low light. And, of course, because it's ultrasonic, auto-focus is speedy.

I'd recommend this lens to anyone, but if you're relatively new to digital SLRs, and you have purchased an EOS 20D kit with the EF-S 18-55, I'd highly suggest the EF-S 17-85 as your next lens. It's quite versatile (a great lens to keep on your camera when you're not doing anything specific) and will let you better evaluate the camera. Remember, this is an EF-S lens (as opposed to EF), so it's intended for the APS-C sensor of the EOS 20D or EOS 300D.
3257554
Let me just say that I have compared this to the 14-24G lens having obtained the 16-35G first.  I live in South America and set up a tripod with my D800E mounted to test both lenses.  I took some shots of some Andean ridges and buildings from my 7th floor apartment balcony, and I can tell you that per the copies that I have, the 16-35 will match or beat the 14-24 in center sharpness from F5.6 upward until F11.  Where the 14-24 shines is in extreme corner sharpness and I doubt any other lens can match its sharpness in the extremes of the FX frame.

The reason I mention the above is because after much field use, the 16-35 is the best and most practical wide angle in terms of weight, option for filter use and ruggedness. When you use the 16-35, stay away from anything less than 18mm due to rampant distortion, but apart from that, just shoot as wide as possible with the 16-35 and then crop out the border distortion in post production and you'll have shot comparable to or even exceeding the shapness and contrast offered by the 14-24.

Frankly, I was going to sell my 16-35 once I received the 14-24, but despite the rice and beans I'll have to eat for the next few months, I'll keep the 16-35 for the majority of my wide angle opportunities--my "walking around" lens so to speak.  I'll keep the 14-24 for those special situation landscape and special event shots where I have time to use a tripod, cable release, MirrorUp and all other user precautions to maximize the full capability of the 14-24.

The 16-35 is a tremendous wide angle at a great price and when used with a little forethought and the post production work that you would do anyway with RAW files, you will not be able to discern any difference between it an the renouned 14-24.  I highly recommend the Nikkor 16-35mm G lens.

Note: After I posted the above review, it occurred to me that I should have used the word "central" instead of "center" sharpness.  I may have implied that only the very center of the frame was sharp.  Actually, the ENTIRE frame is very sharp and comparable to the 14-24, expect for the borders and corners.  This distinction is important because why would anyone favor buying this lens if only the "center" was sharp!
4528570
I bought this lens for my Olympus E-510. It's quite substantial and feels well made, but it feels well balanced well with the Olympus body and is very comfortable to work with.

The lens focusses very quickly - presumably this is the Sigma HSM in action. In low light the wide aperture certainly improves the brightness of the viewfinder in these smaller Olympus SLRs.

Interestingly, Sigma included a note with my lens telling me that one should select Autofocus or Manual focus on both the lens and the camera, but even then one cannot overriden Autofocus with Manual focussing. However, on the E-510 I have had no problem at all overriding Autofocus by simply holding shutter release halfway while manually adjusting focus.

I wonder if the latest firmware upgrade has brought this improvement. I doubt it - I expect that Sigma are referring instead to the published 4/3 standard and that, in practice, Olympus enables a more flexible approach.

The manual override is certainly useful in low light, when even the fast lens does not enable Autofocus to do its thing.

And the results? I'm more than happy. Even wide open, the lens is sharp. Certainly for anyone currently using the Olympus kit lenses you'll feel no difference in quality with this lens. Indeed at f8/f11 it's marginally sharper than the kit Zuikos, I think.

The slight telephoto angle is great for candid shots - not as tight as a real portrait lens, but just long enough frame the subject more tightly than with a traditional 50mm standard lens.

In short (or in slight telephoto, if you prefer) this is a winner. I wouldn't hesitate to suggest it.

And finally ... I can hardly wait to try this with the EP-1.
595146
It was really sad that EF-M 11-22mm lens is not released in US market. Through Amazon, I got this lens from Korea (surprisingly).

When I tested this camera for landscape photos under severe conditions, such as capturing the sun directly, after sunset (much less light condition), etc.. Its flare & ghost control was really amazing. It was even better than regular EF lenses. Also the image quality by 11mm focal length was so great. I could not realize the distortion of image. The canon did the great job on this lens.

The only downside is the price. Since it was not released in US market, it is still more expensive than other EF-M lens. However, if you are serious about the landscape photos, I recommend it. The color along with its performance is great.
217481
Along with the 70-200 f/4 IS L, this lens is always in my backpack when I'm doing travel photography, here is why:

- Lightweight, you basically don't feel it in your backpack.
- Weather sealed when used with a filter.
- Very fast autofocus.
- No purple fringing like I used to have with my Canon EF-S 10-22mm.
- Distortion is moderate.
- Has 77mm filter diameter, with is the case for a lot of Canon lenses.

Its biggest competitor is the Canon EF 16-35 f/2.8 II (or I) but I personally don't need f/2.8 with this kind of travel around lens. If I want a nice bokeh at a short focal, I will use my 35mm f/1.4.

If you want to see real situation samples, just check my blog and website:
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Emmanuel.
2042820
I Got this lens back in Dec. and wanted to use it a lot before leaving a review. I own this one and the canon version and honestly This is a better deal for the fact the construction of it is better. The canon version is made of cheap plastic and doesn't hold well for the active or abusive photographer,it's great if you're just a hobbyist photographer and you like the peace of mind of an IS lens. The Tamron lens has been through a lot of punishment and hasn't broke yet  (including being dropped, not recommending you drop it though.). The telephoto zoom works great ( I got great detail of the super moon back a few months ago, I was shocked at the amount of detail of the moons craters I got.) Sports, wild life and portraits come out great, though if your reliant on the image stabalizing lenses than this takes time to get used to. I have used this lens on a canon Mark II 5d and also on a canon T1i. the out come is the same for a full size sensor and c-size. Just note that on the c(smaller)sensor you tend to get a little dark fringing. Auto focus is a bit loud but fast, and works well on a 2x telephoto extender.....