Canon EF-S 10-22mm lens
I heard James Nachtwey speak earlier this year. In Q&A, someone asked the inevitable equipment question. Incidentally, I think that if you're in a position to ask James Nachtwey anything about photography and the best you can come up with is The Equipment Question it displays, at the very least, a certain stunted curiosity. Anyway, Nachtwey said that the longest lens he ever uses is a 50mm.
A little focal length theory: the Canon EF-S 10-22mm lens is specifically designed for Canon DSLRs with APS-C sized sensors. These sensors narrow the field of view and effectively multiply the focal length by 1.6x. Thus, the 10-22mm lens on a 30D like mine is equivalent in field-of-view terms to the EF 16-35mm f/2.8 L lens on a full frame Canon 5D. On full frame cameras, focal lengths below about 15mm are getting into fisheye territory. With the cropped sensor cameras, a 10mm lens has an angle of view around 97° horizontally.
When you shoot a wide angle lens with a field of view this wide, you obviously get a lot in the frame. My experience, when I first got this lens, was that I ended up with a lot of nothing in the frame. It takes some time to appreciate how close you have to get in order to fill the full frame with interesting elements. I think I spent about six months making mostly really poor shots with my 10-22. Today, I feel like I pretty much see the world in extreme wide-angle.
To compose successfully at wide angles, you have to be aware of several things. Firstly, the "fill the frame" rule still applies, it's just much more challenging to do. Telephoto lenses bring distant things close. Wide angle lenses make close objects appear far off. If you want to fill the frame with someone's head at 15mm, you're literally going to be standing toe-to-toe with them.
Secondly, you always have to think in terms of foreground, middle-distance and background, because it's very hard to eliminate any of those elements with a wide-angle lens. Telephoto lenses foreshorten the perspective of a shot, making the distance between the foreground and background appear compressed. Again, wide angle lenses do the exact opposite - they exaggerate the distance between the foreground and background. Strong wide angle compositions do something with each of these elements and lead the eye through or into the photograph.
The composition below is a good example. It has something in the foreground (the fence), interest in the middle distance (telegraph pole and stable) and an interesting background - the texture and contrast of the clouds against the sky.
The only element of depth that you can really eliminate with a wide angle lens is the background, and you do that by composing with the focus of the image on a strong foreground element. The coffee cups image below is one example.
I often describe the 10-22mm lens as "two primes in one" rather than a zoom. The zoom range is pretty short and the appreciable visual difference really comes down to whether you framed the shot with a focal length above or below about 16mm. Below 16mm, this lens can produce some noticeable barrel distortion effects: verticals will dramatically converge when you tilt the camera, verticals near the edge of the frame will bow outwards. Above 16mm, they're pretty minimal.
When used well, wide-angle lenses give an amazing feeling of 'being there' to the images. One example in which I feel that this is really well illustrated is my photographs of the Glasgow Apple Store opening, all of which were shot with the 10-22mm lens. I also find that I often visualise in black and white with this lens, because the images tend to afford a very photojournalistic feel.
Another strength of these wide angle lenses is handholdability. The field of view of a lens partially determines the minimum shutter speed you require to hand hold it. The 1/$focal_length rule is the shorthand expression of the fact that, when you're filling the viewfinder with a small area very far away, any camera movement will have a large impact. It's trignonometry. With very short focal lengths, the impact of slight camera movements is much reduced.
The Canon 10-22mm lens has a maximum aperture of f/3.5 at the 10mm focal length, so it's not an amazingly fast lens. I can hand hold this lens at some very slow shutter speeds and get acceptable results. The image below was taken at 1/15th, but I have others down to 1/6th which are usable. Obviously, 1/15th is never going to stop motion but, for the architectural and urban photography I like to do, that's not usually a problem. This shot is also a good example of composing with interest in the foreground, middle distance and background. Imagine the ornamental crucifix removed - the shot would be nothing without it.
To me, the extreme wide angle lens feels like the most versatile lens I own. Indoors, it can give you room to make a shot that you wouldn't have with almost any other lens. If you want to photograph inside a mail car or shoot environmental portraits, wide angle lenses are fantastic.
I love to photograph buildings. Wide angles are great for getting it all in, but you have to pick your battles carefully. When you tilt a wide angle lens up or down, it starts to have an impact on the vertical lines in the composition - they appear to converge. You can use this to your advantage and make it a feature of the composition, or you can try to correct it either by software or by using a specialised lens. Right now, I just live with the distortion.
Wide angle lenses like these are a bit of a photography boot camp. They're pretty unforgiving of sloppy composition and you have to work pretty hard, both creatively and physically, to get into a camera position that will enable you to fill the frame with interest in foreground, middle distance and background. As I mentioned, my first six months with the 10-22mm lens produced mostly weak shots. Today, though, I think some of my best photography is with this lens.
If you only let me keep one lens from my kit, this would be it.