If your primary camera is a point-and-shoot, you probably have a general idea of the what the phrase "focal length" means, but you may not really have a practical understanding of it. If you have a DSLR, your experience is going to be a little broader, but depending on how long you've been using your DSLR you may still not know exactly when to use that short or long focal length lens and under what circumstances. So regardless of which type of camera user you are, here's a quick overview about focal length and, specifically, when and why you might want to forgo that longer lens in favor of a wide angle.
First let's talk briefly about what is meant by "focal length." Generally speaking, "focal length" refers to how zoomed in or how zoomed out your camera is when you frame your image. High numbers correspond to longer, or more zoomed-out focal lengths, while smaller numbers refer to shorter or more zoomed-in focal lengths. Focal length is an internal measurement—it is the distance between the point of convergence on your lens to your camera's image sensor. So if you have a 50mm lens, then there are 50 millimeters between that point of convergence and your camera's image sensor. This is actually not particularly useful information because most of us aren't in there with rulers trying to measure the internal distance between an image sensor and the point of convergence on a lens, but it's at least interesting trivia if it's not completely practical.
The primary thing you need to keep in mind is that a smaller number equals a wider angle, or "shorter" lens.
Now what does this mean if you use a point-and-shoot camera? Point-and-shoot cameras almost never have zoom factors that are measured in terms of focal length. Instead, you'll see a measurement that looks like this: "5x digital zoom" or "8x optical zoom." This is a different way of thinking about focal length (it's called "zoom ratiio"), so if you're used to thinking in terms of millimeters you may have to reorganize your thinking to work within that zoom ratio system of measurements.
The "x" system is meant to be easier to understand than focal length—it corresponds to an increase in the size of your subject relative to what the camera can see when it is completely zoomed out. So at maximum zoom, a camera with 2x zoom will show a subject that is twice as large as the subject would be when completely zoomed out. And a camera with 3x zoom will show a subject that is three times as large as the subject would be when completely zoomed out.
How does this correspond to focal length? If you spend some time reading about your point-and-shoot camera (usually in the sales material), you can probably figure out how that zoom ratio corresponds to the focal length on a DSLR lens. A camera that has a 2x zoom, for example, has a focal legnth that's equivalent to a 35mm to 70mm zoom lens. A camera with a 4x zoom ratio is equivalent to a 35mm to 140mm lens. So most point-and-shoot cameras start out with a fairly wide angle view of 35mm, and how zoomed in they can go depends largely on how high that zoom ratio is.
When to use a wide angle lens
Wide angle lenses are good lenses to have on hand if you often shoot big, sweeping scenic scenes such as landscapes or cityscapes. But they're also good for the opposite situation—very small, enclosed places such as small rooms are also great candidates for wide angle lenses because you need that wide angle of view in order to capture more of the room in situations where you can't physically back up enough. So let's look at a few examples of images that were shot with wide angle lenses so you can see exactly what I mean.
'Passing Skies' - Black Point, Penmon, Anglesey by Flickr user Kristofer Williams
This is a landscape that was shot at 10mm. This photographer needed a wide angle of view in order to show you detail in this very big, sweeping scene from the texture of the rocks in the foreground to the lighthouse in the distance. Without that wide angle, this image would have been a lot tighter—maybe just the tidepool in the center of the frame to the lighthouse and part of the sky. That might not have been a bad picture, but it would have had a completely different feeling than this image has. In this image, you get a strong sense of that vast, open space—you can almost feel the breeze as you stand there drinking in the cold ocean air. A zoomed in shot of the lighthouse would show you more detail but it wouldn't give you that same sense of enormity.
Now let's take a look at another example:
_DSC1912 by Flickr user Oleg Green (lost)
In this image, a wide angle of 15mm was used to capture three subjects from across a small space. Without a wider angle it would have been difficult to get them all in the frame, but it also would have been impossible to capture any context along with the subjects.
You can use a wide angle lens to do something similar in any indoor situation—let's say you want to capture the interior of a room in its entirety. You would need to use a wide angle lens and stand against a back wall in order to achieve that. If your focal length short enough you should be able to capture even a very small room as long as you have your back against the wall.
One thing you'll find when using wide angle lenses is that you can create a certain amount of distortion in your subject. This may or may not be a good thing depending on your perspective. I'm sure you've experienced what happens when you shoot a human face using a short focal length—you'll get a disproportionately large nose and forehead and very small ears. This can give your photo some comic appeal, which is great for shooting animals like dogs or horses, but a particularly vain person may not appreciate being presented with features that are much bigger than they are in real life.
You can also use distortion to your advantage—let's say you're photographing a scene and you'd like to make it look bigger than really it is. You can use a wide angle lens to exaggerate the distance between objects. This is basically the same thing that's happening when you use a wide angle lens to photograph a human face—the nose looks larger in the image than the ears do because the distance between them is exaggerated. If you use the same lens to shoot scenery—let's say farmland with outbuildings—you can actually make the scene look larger because the distance between each of those outbuildings will be exaggerated. Real estate photographers frequently use wide angle lenses to make a property seem larger in a photograph than it does in person.
DSC_9567 by Flickr user Davi Alexandre
You can also use your wide-angle lens to photograph detail. When you get very close to your subject using a wide angle lens, it has the effect of magnifying whatever detail is closest to the camera. You can use this technique to make the eyes of a fly look extra large, or to simply force your viewer's attention onto one important detail over the other less-important details.
Wide angle zoom lenses are a great way to get your feet wet with those wider angle shots—purchase a wide angle lens zoom lens in the 17 to 55 mm range and then you'll have an option for either shooting wide of for zooming in a little bit. Not every subject is going to be flattered by that wide-angle perspective, so a little bit of flexibility can really help. Remember though that zoom lenses that do come with some drawbacks, such as a variable apertures and slightly lesser-quality images, depending on the focal length and your budget. Wide-angle prime lenses do generally produce better quality images, but you have to keep in mind that the kind of quality differences we're talking about are not drastic and your tolerance for them is purely dependent on the sort of photographer you are. Some photographers are very particular about achieving maximum sharpness and freedom from aberration, while other photographers are happy to live with a little bit of minor quality degradation because they just don't print larger than 4 x 6 or display their photographs professionally. So whether or not you'll be happier with a prime or wide-angle zoom lens is really up to you. Just start with a price point you feel comfortable with, spend a lot of time shooting and plan on upgrading when and if it makes sense.
- When to use a wide angle lens
- Big, sweeping scenes
- Small rooms
- To create distortion
- To exaggerate the distance between objects
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