You want a wide angle lens (35mm focal length and wider on a full frame DSLR camera) or an ultra-wide angle lens (24mm and wider) to photograph the big scene, to capture a smaller scene in a limited amount of space or, my favorite use, to create a close-to-subject perspective that gives the viewer a sense of presence in the photo.
Since most of us have at least one general purpose/standard zoom lens that has wide angle focal lengths built into it (a 17-55mm lens or a 24-70mm lens for example), an additional wide angle lens is needed to gain even wider angles of view, for better image quality or perhaps for a wider aperture. If your standard zoom has an f/2.8 max aperture, you will be looking for a fixed focal length/prime wide angle lens to get the wider aperture. If you have a high-end normal zoom lens, finding better image quality might be a challenge.
I very frequently encounter the need for focal lengths wider than those in my standard zoom lens. My personal need for these wider angles of view can be either to get subject in the frame with a limited working distance or to utilize a closer perspective of the same primary subject framing than my standard zoom can give me. The latter is a technique frequently used in landscape photography - emphasizing a foreground subject against a vast in-focus background. And in these cases, a wide angle or ultra wide angle lens is the answer.
Specific needs for the wide angle lenses include landscape, real estate/architecture and interior photography. Interiors include those of a building, vehicle, aircraft, etc.
Addressing APS-C Wide Angle Lenses First
The selection of wide angle lenses with focal lengths wider than the 17-18mm found in normal zoom lenses is rather limited for APS-C format camera owners. Canon has one rectilinear (not a strongly barrel-distorted fisheye) zoom lens. Fortunately, it is a good choice.
Here is what the APS-C 10-22mm focal length range looks like:
The Best Canon APS-C/1.6x Wide Angle Lenses - My Recommendations
An Overall Nice Lens with Ultra Wide Angle Focal Lengths
The Canon EF-S 10-22 will give you decent image quality in a small, light package with a modest price. Autofocus is Ring-USM-driven. The wide angles from this focal length range will impress most photographers currently using the 17- or 18-something general purpose zoom lenses. The EF-S 10-22 complements most of these standard lenses very well.
2. The Decision Quickly Becomes Difficult
Go with a Sigma or Tokina ultra-wide zoom? Or go with a prime lens?
The Tokina 11-16 f/2.8 Lens (new version is "II") will give you a nice focal length range and a wide f/2.8 max aperture. Build quality is very nice.
The Sigma 8-16mm f/4.5-5.6 DC HSM Lens will give you incredibly-wide focal lengths in a solidly built HSM-AF lens.
Canon has some impressive prime lenses. For specific prime lens recommendations, refer to the full frame wide angle lens recommendations below.
The Full Frame Wide Angle Lenses
Excluding the excellent Canon EF 8-15mm f/4 L USM Fisheye Lens, Canon currently has twice as many full frame wide angle zoom lenses as APS-C wide angle zoom lenses: 2. Fortunately, both are very good options.
Full frame format camera owners have many more prime lens options available for their wide and ultra-wide angle needs. There are more full frame lenses as wide or wider than the 24-something standard zoom lens typically used - and lenses with wider apertures. APS-C format body owners can of course use these lenses (they will work great), but most do not provide an angle of view wider than the 17- or 18-something APS-C standard zoom.
Here is what the full frame 16-35mm focal length range looks like:
The Best Canon Full Frame Wide Angle Zoom Lenses - My Recommendations
Canon's Best Ultra-Wide Zoom Lens
The Canon EF 16-35 L II is a professional grade lens with excellent weather-sealed build quality, Ring-USM autofocus and very good image quality. The f/2.8 aperture makes this THE wide angle lens to have for low light events (anything indoors) and for sports. This focal length range is very useful and complements most normal zoom lens focal length ranges very nicely (with nice-to-have overlap).
Almost Canon's Best Ultra-Wide Zoom Lens
There are not many significant differences between the 17-40 L and the 16-35 L II. The biggest difference is the 1-stop max aperture and the second biggest difference is the price - the 17-40 L is a bargain. The 17-40 L shifts the focal length range slightly longer and weighs slightly less. Shared is great weather-sealed build quality and image quality is similar beyond f/5.6.
If your requirements do not include a range of focal lengths in the same lens, you have significantly more wide angle options available to you. I will list some prefered fixed focal length autofocus lenses in focal length order.
The Best Canon Full Frame Wide Angle Prime Lenses - My Recommendations
Ultra-Wide Focal Length, Excellent AF, Excellent Weather-Sealed Build Quality, Small Size
This solid little lens will give you the widest non-fisheye angles of view available in a Canon full frame lens. The perspectives at 14mm are impressive. Image quality is great. The convex objective lens element prevents the use of standard threaded filters.
Ultra-Wide Aperture, Excellent Image Quality, Excellent AF, Excellent Weather-Sealed Build Quality
F/1.4 is the widest aperture currently available on any lens wider than 50mm. And this ultra-wide aperture can make a big difference when the light is dim.
This is usually the lens I take when the night sky is on my subject list. While some coma will make the stars in the corner of the frame appear comet-shaped, the wide angle focal length combined with the wide aperture create nice images at night.
The wide aperture can also give your images a blurred background look that sets them apart. This is a great lens overall - including great image quality.
Small & Light, Image Stabilization, Excellent AF
The lens will not take up much weight in the bag and will not burden your shoulders carrying it. But, it delivers very good performance with image stabilization there to help.
Small & Light, Image Stabilization, Excellent AF
This lens is nearly identical to the 24mm f/2.8 IS - just in a 28mm focal length.
Sigma's Best Lens Ever?
The 35 f/1.4 is the best Sigma lens I've used as I write this. It delivers best-available f/1.4 image quality in a solidly built body with good-performing AF. It looks good too.
Ultra-Wide Aperture, Excellent AF, Great Build Quality
While this lens is getting some age to it, it is still a good choice. You get Canon L lens build and performance qualities in a modestly wide angle focal length. Stopped down somewhat, this lens delivers razor sharp images.
Small & Light, Excellent AF, Wide Aperture Combined with Image Stabilization
As I write this recommendation, the 35mm f/2 is Canon's widest aperture lens under 200mm to have image stabilization. This small, light lens is able to capture sharp images under extremely low light levels - with a still subject. This lens was delivered not long after the 24 f/2.8 IS and 28 f/2.8 IS - it is very similar in both build quality and performance - and this is a good thing.
If your requirements do not include a range of focal lengths in the same lens OR autofocus, you have even significantly more wide angle options available to you. I will list some of my prefered fixed focal length, manual focus-only lenses in focal length order.
The Best Canon Full Frame Wide Angle Manual Focus Prime Lenses - My Recommendations
Impressive Build Quality, Great Image Quality, Accepts Threaded Filters
This may be the widest angle Canon-mount lens to accept threaded front filters. The filters are large, but ... landscape photographers especially appreciate this feature. The 15 f/2.8 has build quality typical of Zeiss ZE lenses - impressive. Image quality is also very good.
Excellent Build Quality, T/S Movements
The TS-E 17 is very frequently my choice for an ultra-wide focal length need - especially for landscapes. The tilt, shift & rotation movements provide many benefits and the image quality is tops at this focal length. It's built like an L lens.
Impressive Build Quality, great image quality
The Zeiss 21 is an all-around great lens. The focus ring is very smooth, the lens is impressively built and the image quality is superb.
I Love This Lens!
The TS-E 24 L II has the best image quality of any 24mm prime lens I've ever used. Actually, there are very few lenses that reach this level of image quality excellence. Add excellent build quality and the tilt, shift & rotation movements and you get an overal awesome lens. This level of excellence comes at a price. And using the tilt-shift features can take more time than point-and-shoot.
Ultimate Build Quality, Excellent MF Ring, Great Image Quality, Ultra-Wide Aperture
I'm sure that the significantly less expensive and even sharper at f/1.4 Sigma 35 f/1.4 has put a dent in the sales of this lens, but the Zeiss remains a great choice and is built for the long haul. This lens has impressive build and image quality.
For more wide angle zoom lens options, read the Canon General Purpose Lens Recommendations page.
Visit the Canon Lenses page for more lens recommendations.