A friend on Facebook just asked me for advice about wide angle lenses, and rather than relay what I know to another individual, I thought I’d post here for him and anyone else who’d like to hear my thoughts. My experience is based on having owned the Nikon 14-24mm f/2.8G ED AF-S Nikkor Wide Angle Zoom Lens and the Canon EF-S 10-22mm f/3.5-4.5 USM SLR Lens, both of which were great in their own ways, though the Nikon is a full frame lens and the Canon is not. I suppose we should start there.

Most DSLRs are ‘crop frame’ cameras, meaning that the size of the sensor is smaller than that of a full frame camera, which has a sensor the size of a 35mm film negative. The benefits and disadvantages of full frame vs crop frame are topics for another discussion, but this difference has a profound influence on the image you get through a wide angle lens. The lens projects a circle onto the sensor or film plane, creating an image that is a rectangle as shown above. With the angle of view provided by a 24mm lens, a full frame camera includes much more of the scene than a crop frame camera does, as you can see. This is why most lens makers offer super-wide crop frame versions such as the 10-22mm I used on my Canon bodies. The 40D was a 1.6x crop factor camera, which meant that the full-frame equivalent at 10mm on that EF-S lens was 16mm. In other words, you’d see the same thing at 10mm on the 40D as you would at 16mm on the D700.

So the first consideration about which wide angle lens to buy is if you need a crop frame version or not, and if you don’t know which category your camera body falls into, you need to find out. If you’re unsure, you probably have a crop frame body, since full frame cameras tend to be quite a bit more expensive, and the vast majority of DSLRs out there are crop frame models. Also, the list of full frame camera bodies is pretty short. I believe this is it at the moment: Canon 1Ds Mk III, 5D and 5D Mk II; Nikon D3 series, D700; and Sony Alpha 850 and Alpha 900. If you don’t have one of these bodies, you almost certainly have a crop frame sensor. I’m now bracing myself for the nasty emails informing me of which full frame models I’ve forgotten to include.

To further complicate things, not all crop sensor cameras are the same crop factor. Canon makes some pro cameras that are 1.3x, but most consumer models are either 1.5x or 1.6x, which just means that you multiply the focal length of the lens by that number to find the effective focal length, or the 35mm film equivalent. Thus, a 20mm lens on a 1.5x body is equivalent to (20 x 1.5) a 30mm lens.

How Wide is Wide?
Once you know how much of a wide angle lens’ focal length you’ll actually see on your camera body, you can decide what you need to buy to get your desired effective focal length. In the old days, the wide angle lens class started around 35mm and went down from there to the region of 10mm or so for a distinctive fisheye look. But as just explained, a 35mm lens on a 1.5x body gives a focal length equivalent of 52.5mm, pretty much a ‘normal’ view, or one that replicates fairly closely what we see with the naked eye, but without the benefit of our amazing peripheral vision. So to get a proper wide angle lens on a crop body, you need to start at at least 20mm, which is why the most common zoom lenses top out in that neighborhood and on the wide end of the zoom range go much wider, to 10 or 12mm.

The Wider The Better?
Not always. Sure, a very wide lens allows you to get much more of what you see into your image, but the wider you go, the farther away your subject appears to be. This can be undesirable if you want, say, to make a landmark your subject, and you want a lot of its surroundings in your image, so you go very wide only to find that your subject has gotten so small you can barely see it. Still, you will sometimes find yourself standing in a spot that makes great use of 14mm. It all depends on the individual situation.

Go rectilinear!

[Edit--please see the first comment from Tyler for more information!]
The wider you go, the more at risk your image is to showing distortion of straight lines known an pincushioning or barrel distortion. Look at the image above and notice how the towers of the Golden Gate Bridge do not appear to be straight. Even on pro lenses such at the Nikon 14-24mm, when you zoom out to the widest setting, you may get some of this affect, which can look quite odd when you don’t want it. A fisheye lens does not have rectilinear correct in its design and thus exaggerates this barrel distortion to give its very distinctive curvilinear style of image. The good news is that often you can correct this distortion in Lightroom, or manually in Photoshop using the Skew function.

The Filter and Hood Question
Because crop frame wide angle lenses have to view such a wide angle to deliver an focal length equivalent of 16mm or so, they are limited to how large a lens hood and how thick a filter you can use without having either of those items affect the image. Filter makers have developed very good quality slim filters for these lenses, but be prepared to pay extra for these flatter filters that do not cause vignetting on super wide lenses. It is also very difficult for lens hoods to do their jobs on wide lenses because so little of the hood can extend beyond the front element without causing the same problem, vignetting (darkened areas around the corners of the image). Lens hoods have two main functions, the first being to keep light from striking the lens at such an angle that it refracts off the elements inside the lens to create light spots called lens flare, and the other being to protect the front element from touching anything that might damage the glass. This last concern is important because super wide lenses generally focus very close to the front element and allow you to place the camera VERY close to your subject for specific effects.

The above image was made with the Canon 10-22mm on a 40D with the front element of the lens about half an inch from the engine. You may notice that there is fairly shallow depth of field, especially for a wide angle lens, which as a class of lens generally has very broad depth of field. That’s one of their characteristics, even when used at large apertures. Getting the camera close to the subject is one way (the only way, in my experience, without using a wide angle tilt shift lens) to create a wide angle image with shallow depth of field. But because of the small lens hoods, you must be very careful not to get so close to your subject that your subject doesn’t touch the front element. This is especially tricky when getting used to your new wide angle lens and you’re looking through the view finder. Several times when I first started using the 10-22mm lens I was moving closer and closer to my subject with my eye at the view finder, thinking from that view I was plenty far away, only to make the exposure and take the camera away from my face to learn that the lens was less than an inch from the subject. Since most newer DSLRs come with some form of Live View, allowing you to compose your image using the LCD screen on the back of the camera rather than by looking through the viewfinder, I highly recommend using this feature for images that require the camera to be close to the subject. When you’re holding the camera away from your eye and using the LCD screen, you can also see how close you are to colliding with the subject.

So, which lens, then?
As I said before, the Canon EF-S 10-22mm is a great choice for users of crop frame Canon bodies such as the Canon EOS 7D, the Canon EOS 50D and the Rebels, such as the Canon EOS Rebel T2i. This lens will not work on full frame Canon models, such as the Canon EOS 5D Mark II and the original 5D because the image circle the EF-S lens delivers to the sensor is not large enough. I’ve also used Canon’s 16-35mm f/2.8L II USM Ultra Wide Angle Zoom, which is fantastic, but which on crop frame models only delivers an equivalent of 25mm on the wide end.

Nikon makes two lenses that are comparable to the Canon’s 10-22mm for use with models such as the D90 and D5000. First is the Nikon 12-24mm f/4G ED IF DX Nikkor, which has a great reputation as a fantastic crop frame lens. In 2009 it was replaced in Nikon’s lineup by the Nikon 10-24mm f/3.5-4.5G ED AF-S DX Nikkor, which I’ve not used but which I’ve heard good reports about. Apparently its lower price tag is due to cheaper construction than the 12-24mm, which was solid as a rock and had very good build-quality. However, the new version does go 2mm wider, which though not much, might be compelling for you. Perhaps some of those who read this blog will chime in on their experience with either lens.

Lens makers such a Tokina and Sigma also make super-wide crop frame lenses, and though I’ve not used lenses from either company, I know several pros in the MotoGP paddock who choose these over Nikon and Canon alternatives. An affordable option to the Canon and Nikon choices is the Sigma 10-20mm f/4-5.6 EX DC HSM Lens for Canon Digital SLR Cameras and the Sigma 10-20mm f/4-5.6 EX DC HSM Lens for Nikon Digital SLR Cameras. A friend has this for his Canon Rebel and likes both the image quality and the lower price tag.

Zoom, zoom, zoom.
All lenses mentioned so far are zoom lenses, and while some people swear their prime lenses are sharp and/or have fewer defects in image quality, modern zoom lenses are so good it’s hard to pass up the convenience they offer when it comes to framing your shot as you wish. I highly recommend making a good quality zoom lens your first wide angle purchase, if for no other reason than to figure out what focal lengths you use most often. If the lenses listed here are too expensive, then by all means look for a used prime lens around 20mm to experiment with before making an expensive commitment to one focal length. But if you get a zoom lens and find you always use it at its widest setting, consider trading it for a prime lens at that focal length, which just might save you some money and even give you better performance.

Or…
Just to throw the cat amongst the pigeons in this discussion, I’d like to tell you about a wide-angle alternative that I use all the time. This technique won’t suit everyone because it requires a tripod with a good panning ball head to work really well, and it results in much larger files than most people need. But please have a look at this image, a version of which I posted not long ago:

This is a panorama I made using my 70-200mm lens turned to portrait orientation. I made five exposures and combined them in Photoshop, each overlapped by about a third of the image, so that Photoshop’s Photomerge function could take them all and create a seamless composite.

The result is an image 8400 pixels wide with incredible detail, much more than I get out of a single exposure. I can crop the image as needed, to the equivalent perspective if what I’d have achieved with a wide angle lens but have much great detail. Since I make large prints, this is a great technique for my needs. Though I love my Nikon 14024mm lens, it does have drawbacks. Single exposures sometimes lack the resolution I want for large prints. I do get some barrel distortion in certain situations. Due it its huge, rounded front element, I can’t use a circular polarizer when I want to. But by using a longer focal length lens turned to portrait orientation, I can get the same area of view in a image by combining multiple exposures with greater detail, not barrel distortion, and I can use my CPL filter if I want. As I said, this technique isn’t for everyone. It requires extra equipment, extra work, and creates larger files, which can be a pain to work with and manage. Bit I wanted to show you in case its benefits appeal to you, since we’re talking about getting good images with a wide angle of view.

Please comment if you have experience with any of the lenses I mentioned or your own advice for fellow shooters looking to explore the world of wide angle photography.