Instruction: Generate an answer to the question by utilizing the information contained in the document.

Input:
Question: how well would this do to shot a large group of people. i am shooting a wedding and they would like a picture of all the guests.
Document: This lens is a great option for any Canon owner of a 7d and below. The build quality may not be "L" standards, but picture quality is outstanding! I use this lens for large group shots, indoor shooting, street shooting, and anything/everything to create that "WIDE" look. If you are looking for a wide angle for your bag, this is your best option.
NO BARREL DISTORTION. This means that a straight line in the real world will appear as a straight line on the picture. This makes it a prima facie excellent choice for architecture work.However beware: when shooting groups of people, the faces on the sides of the picture will appear elongated. This does not mean you can't use the lens for group shots (I do), but I find myself adding some barrel distortion in post-processing for the people on the side to look normal.
I love this lens. The USM with full time focus is great. I don't think I would by a lens without it. Build quality seems good. Barrel distortion is minimal, very well controlled. Color and contrast are great. It's so wide that you'll take a picture of your toes if your not careful. I use it mostly to bring a different perspective to landscape and architectural photos. At the wide end with subjects up close it really does distort. Cute with puppies, but terrible for people.
I typically shoot only L lenses and my shots are indoors at athletic events. However, many times I'm right on top of them or shooting a group of people with no room to get back in the distance . . . this lens filled that void for me. Great pictures.
I have been using this lens at weddings and simply love it! While there is a lot of distortion on the edge at 10mm (which should be expected, but still stinks), it makes for some unique images, especially when trying to take in the entire "scene". I have also used it to get large group shots when there's no room to back up. At one wedding, I overheard someone saying "that must be an awfully wide lens 'cause I can't get everyone in!"
It is not! It is an ultra-wide angle lens and as such does not do well with portrait shots, unless you have a large group or are looking for a portrait with a large amount of (in focus) background.Once you get to the 4.5 stop, low light indoor shots become trickier, this isn't a fast lens.What you should know:I bought a standard tiffen UV filter and didn't see noticeable vignetting.
If you like an artistic style and really want to get a wider picture, then you will certainly not be disappointed with this lens. The color and clarity of this lens is fantastic and it's a blast to use! Just be sure to practice with it first if you take shots with people in it...as it will distort.So much fun and a must have for any non traditional photographer!
I owned this lense for about a year and it does take nice, clear pictures. It is also a handsome lense with a strong, sturdy build that is still very light. However, it certainly has its flaws. First off, the barrel distortion at 10 - 12mm is almost completely unbearable if you trying to take a picture representative of what you are seeing. It flattens out the scene considerably making objects - like people - look one dimensional. Women - it straight up makes you look fat.
I'm fairly new to photography, but I wanted to write a review for people out there that may also be new. This lens is worth the purchase and it doesn't take much to learn to use it. The wide angle setting is great, and focusing on close up works well too. I have found the picture quality to be even sharper than some of my other lenses. The distance focusing ring is an added plus.
But when used for landscapes in ideal lighting its performance is very unacceptable. I was expecting barrel distortion so it was no surprise to see it and I know there are programs to fix it. I also knew that some people reported vignette but I wasn't expecting it to be as bad as it was. And the picture was very soft even at the centered focal point. These flaws along with the construction do not justify the expense. Some people reported the lens performing well out of the 10mm range.
Answer: Shooting groups of people with an ultrawide works well, but people on the extreme edges of the frame will appear stretched out. It's also not the fastest lens, especially at the longer focal length, so you will most likely need a flash if you're planning on shooting indoors. It's a fun lens, but you may be better off using a faster wide/normal lens, such as the 17-55mm 2.8, or the sigma 18-35mm 1.8.