Super sharp. Really like this lense and use it ...
345489
Super sharp.  Really like this lense and use it for almost all situations.  Only downside is that its a bit heavy.  I just use it with the HLD-6 grip.
1229337
This is a great Lens at a great price and makes a great gift for those that do not know what to get the photographer in your life.

With my husbands personal shooting experience he says that this lens is  sharpest at f5.6 - f8. but the sweet spot of sharpness is a bit smaller.

Flare is nicely controlled and most significant in the corners.
Focus - Performance is good, even in low light. The focus speed and accuracy are quite good. The focus ring does turn on this model. He has pointed out that front element does not turn while focusing, not sure if that would be an issue for others.

24mm performance useful in some situations. He has found that close in  can be acheived. I have read other reviews that claim close up 24mm performance is not good, but he says that he has found that this serves just fine.

Overall - a good choice in a useful focal range and a good value. I would recommend this lens.
When used correctly, this lens provieds very good results.
2136085
Nice, compact, fast, and sharp fixed lens (equivalent to 50mm on full-frame/35mm). Minimum focus distance is about 11". Great lens!!!

PROS: Razor sharp with lightning fast autofocus. Works beautifully on PEN E-PL5 and -PL7. Good contrast, color rendition, and great bokeh. This has become my main working lens - sharper than Oly. 17mm and kit zoom 14-42mm at 25mm. Paired with the 45mm which is almost exactly the same size and a wide angle, you have a very compact and high quality setup of fixed primes.

CONS: Plastic construction and non-weather-sealed. Bought this as international so it lacks US warranty. However, this saved $100 and lack of warranty is not such a big deal since if lens doesn't work for you, or is defective, it can still be returned within Amazon's return period.
105485
Super sharp.
This is the second set I purchased. Bought them for my college son
2527836
Very good lens.  I like all the features it offers.  It has power zoom, with *three* speeds, and an option to switch to a manual zoom.
The power zoom is a bit slow but it's a good thing.  It adds more professional feeling to my videos.
I use it with a Sony NEX-3N.  The power zoom lever activates the lens but if you try to zoom in, aaaaall the way there, I'd recommend to use a remote control.  When the lens is fully retracted, the smallest vibrations from a hand, are magnified and visible.
The lens takes great still pictures too.  Very crisp and sharp.  I guess the quality of the glass is very good.
It is a bit heavy but it's a small price to pay for superb quality of photos and videos.
My camera came with a 16-50 lens and I liked it.  When I saw how good this lens was - I sold the 16-50.
18200 does everything the other one did and then some.
I was able to take awesome photos and achieve the bokeh effect - blurred background.  One day, a bird sat down on my balcony railing.  She was just posing for the photos.  I've also stopped at the Millennium Park, in Chicago.  Very nice pictures. Take a look.
1792483
The lens is sharp.... Not L lens sharp but sharp. The images look great and the lens is small for its focal range and very light. My only gripe with this lens is that the body mount ( the part that attaches to the lens to the camera) is plastic, so I think there may be some durability problems down the line. Other than that great lens for the price
67016
This one needs a 6th or even 7th Star.  This lens is Very Sharp - only moderately heavy and a true joy to use.  It is the easiest lens I have experienced to manually focus - much easier than for example, the 55-300 Nikon lens that I have.  Great lens - great service from Amazon.
1183998
This lens is very sharp. I tested this out on a Nikon D810 and comparing it to the Tamron 24-70mm 2.8, Sigma 70-200mm 2.8 & Sigma 24-105mmm, it is WAY sharper. Corner sharpness is very good and sharper than any zoom lens. For the price it's a great lens.
1631371
No regrets. Great filming lens (for auto) and it's actually a really sharp image lens. I use it constantly.
4906889
Super fast (F1.4), very sharp over the entire field, 12mm wide-angle (equivalent of 24mm on full-frame), weather-sealed lens for MFT cameras.  Used it on Olympus PEN EPL-5, -7, and M5 mkii bodies (due to its size it feels more comfortable on M5). Great for landscapes and crowds, street shooting, where low light conditions may prevail.  Also should be great for astrophotography although I have not had a chance to try it yet.

PROS: Nicely finished metal body construction with smooth-as-silk focusing ring in manual mode.  Razor sharp lens even fully open at F1.4.  Fantastically small focusing distance, great for popping objects from the blurred background - very nice and creamy bokeh. Auto focus is very quick (at least on OLY bodies). Color rendition is very realistic and the contrast is good in most lighting conditions. No noticable vignetting. Flare is nicely controlled. Comes with a high quality (metal) lens hood and nice plastic lens cap.

CONS: Heavy and large (this is the physics of F1.4 - you need a lot of glass). Significantly bigger than the Oly F2.0 12mm and Samyang models. ~ 4 pixels of chromatic aberration at edges (purple fringing) under high contrast scenes. Autofocus is audible (not loud per say, but noticable). The aperature ring does NOT work with OLY cameras - not the lens' fault so no points deducted.
A bit expensive as compared with other lenses in this class - included lens bag is disappointing lightweight nylon.

Night shots below were done on an EPL5 with ASA 400 and F1.4.
606592
I've had this lens for a few months now, but waited to review it until I'd had a chance to really put it through it's paces. Got to do that a week ago in Tucson at Pima Air Museum. I use to use the older Sigma 10-20 f/4.5-5.6, and loved it! But, there were times when I wished I had just a bit more wide.  I've included 2 photos from the trip (compression killed the sharpness). The side view is at 16mm, the nose on is 8mm.

To me, it seems overall sharpest from 10-16mm. At 8-9mm, the center is still sharp, but there is some fall off the further out you get. mind you, at the widest, I tend to be really close to my subject, so some falloff makes sense. Used at 8mm, but to a further subject, the DOF is deeper.

This lens (like all UWAs) really aren't for everyone. They take some getting used to so you don't end up with comical distortion. If you are willing to take the time to practice with this lens, and learn to use it, it can be pretty awesome!
4200146
I really like this lens. It's what's on my camera by default. I no longer use my kit 18-55 or 70-300 telephoto. I do, however, still lean heavily on the fixed 50 f1.8 (a very nice lens, by the way).

So... the pros and cons and inbetweens:
1. WTF... it's the same price as the Nikon and Canon, but those lenses have vibration compensation (not needed in a sony lens, since VC is done by the camera body). So why isn't it cheaper???
2. It's not so good at acquiring focus. Often skips past and then backs up. If you're at inf and suddenly switch to close up then I hope you aren't shooting a moving target (like a toddler...)
3.  It's fast at focusing and pretty silent... so even if it's not accurate it moves quickly enough
4. F3.5 ain't bad. Nothing like the f1.8 noted above, but hey, the zoom range is spectacular
5. it comes with a hood. The hood, when positioned out of the way (backwards) blocks the focus ring for manual control. Minor point, just mentioning it.
6. Power hog (relative to the fixed lens). Must be the motor.

So, in summary, this is a value lens. I doubt you'll find better zoom range and speed in this price range.
188636
I think this has become my favorite lens so far... macro and protraiture in the same very sharp lens.
3612798
I purchased this lens to go with my Canon EOS 20D digital SLR, which I inherited from a friend who unfortunately had passed away.  The camera came to me with only a wide angle zoom, but most of the photos I shoot are in the normal to telephoto range.  So I chose this lens because of its good zoom ratio, and it's relatively compact size.  The latter makes it a good all-around lens to travel light, such as on overseas vacations.

This lens is really sharp, so much so that I can blow up a selected portion of a photo in Photoshop and it's still pretty sharp.  This effectively comes close to giving me the equivalent of a 600 mm telephoto (in 35 mm film) in a walk-around lens.

Unfortunately, the lens vignettes (i.e. the corners of the photos are dark relative to the center of the photo).  The vignetting is most pronounced in the longer telephoto range.  It is especially noticeable with a background that's uniform in color and lighting, such as a blue or overcast sky.  Further, the darkening is more pronounced in the upper left corner compared to the upper right.  I can correct most of the vignetting in Photoshop, but that program does not deal so easily with the differential darkening between the corners, thus some darkening remains.  (Advanced Photoshop techniques should be able to deal with that, but so far I have not expended the necessary effort).  Because photos I shoot tend to be more varied in color, lighting, and with more detail in the lower corners, the vignetting is not so noticeable there; thus I have no comment at this time re the behavior in those corners.

The lens also has a very heavy front element.  When the lens is on the camera,and that combination is on the strap around my neck, this tends to keep pulling the combination down and then the weight further pulls the lens out into the fully extended telephoto position.  Rather inconvenient!

But for these problems, I have would given this lens a 5 star rating; instead I gave it a 3.

Update: The lens is incredibly sharp.  I took this lens as my only lens on a recent Mediterranean cruise.  While docked in Pireas (Athens) I took a rock-steady, hand-held photo of a distant cruise ship at the 200mm setting -- like a 330mm shot for an old 35mm film guy like me.  The cruise ship was still kinda small, so I cropped the photo in Photoshop to what's the equivalent of about a 1000mm shot (for 35mm film) and it's still incredibly sharp!  Imagine having that kind of telephoto magnification in a camera you can carry around your neck!  On this same cruise, I took lots of other photos at all the focal lengths offered by this lens, and all are good except when I myself messed them up!  Vignetting is still a problem though, and I had to spend a lot of time in Photoshop applying fixes to many of the photos from that same trip: So still a 4 rating.
1899685
I needed a 'normal' lens for my Sony a350 DLSR. I have a few zoom WA lenses that work well but sometimes it is nice to just put on a normal prime lens and let your legs do the 'zooming'.
This lens is the latest (I think) Sigma 30 mm (45 mm full frame equivalent), f 1.4 EX DC prime lens. After testing it on several garden activities I'm pleased with the results.
This lens is very sharp except at f 1.4 and then it's a little soft at the edges. Stopping down to f 4.0 & beyond produced very sharp images w/o distortion. The photos are stunning !! Autofocus was not a problem. Just make sure to use the proper focus zone (I use center spot to focus on what I want to see in the photo).
This lens is somewhat expensive compared to some other f 1.4 prime lenses but well worth the money.
This lens will stay on my camera unless there's a special reason to need one of the zoom's.

Art Logan
937609
This is a really nice Nikkor lens, incredibly sharp, changing from AF to manual focus is done on the fly, great results, it does what it is designed for really well. AF is great in good lighting, it hunts a bit in low lighting conditions. Overall this is one of Nikon's best lenses.
4769588
BEST LENS I have ever used ! I own a Canon T5i and a 70D . This lens is super fast and sharp . I am amazed at how it performs in low light. I own the 18-135 mm , the 40mm pancake, the 55-250 stm and the Tamron 150-600, and this Sigma is now the Icing on the Cake !