Dear Lifehacker, I've got a DSLR that came with a regular zoom lens. It's fine, but I want to get a new lens or two so I can do more? How do I pick the right one? Sincerely, Optically Limited
The lens you get when you buy a DSLR -- generally a standard 18-55mm zoom -- is designed for some level of versatility, but it doesn't capture particularly sharp images, and it doesn't have any special features. When you go to find a new lens, most of your options aren't as versatile but handle specific things very well. Let's go over what types of lenses you can get and why you would want them.
Learn the Lens Basics
Before we get into the various types of lenses, it's important to know a few terms and basic ideas about lenses so that you can understand what they mean when you're shopping around. Lenses are labelled like this: 18-55mm f/3.5-5.6. That designation tells you a lot but doesn't mean much if you don't know a few terms. In this section we'll learn what you need to know to understand how lenses are labelled and what those labels mean.
Zoom Lenses vs Prime Lenses
It's important to know the difference between zoom lenses and prime lenses. A zoom lens does what you might expect: it zooms in and out, allowing you to magnify your subject. A prime lens can't zoom. If you want to move closer or farther away with a prime, you move your legs rather than turning a zoom ring on the barrel of the lens. Why would anyone prefer a prime to a zoom? Primes are often cheaper, offer sharper results, have wider apertures (which means they can take in more light, thus performing better in low-light situations) and generally handle their specific function better than a zoom. That said, for enough money, a zoom can perform just as well and offers more versatility. Obviously, you have an advantage if you don't have to constantly change lenses. Zooms allow you to essentially change the lens -- and therefore the type of shot you're getting -- by zooming in or out. Primes do not.
Both zoom and prime lenses are designated by their focal length. Focal length is often measured in millimetres (mm) and designates the distance at which something is in focus. This definition doesn't mean much practically speaking, so what you want to remember about focal distance is that lower numbers indicate a wider view (zoomed out) and larger numbers indicate a closer view (zoomed in). For example, if you're photographing a small room in a house and you used an 18mm lens, you would likely capture the majority of the room in your image, while you would get very little of the room with an 85mm lens. Primes only have one focal length, and so they're simply labelled as 35mm, 50mm and so on. Zooms offer a range, and so they're labelled as 18-55, indicating that you can achieve a focal length as wide as 18mm, as close as 55mm and everything in between.
Lens titles have two measurements. The first is focal length, as we just discussed, and the second is aperture. Aperture determines how much light your lens can let in. When a lens has a wide aperture, designated by a small number called an f-stop, it captures more light. When a lens has a narrow aperture, designated by a larger number (f/5.6), it captures less. Wide apertures allow you to take photos when less light is available because the lens can see more of the light. Take a look at the photo to the right. The pictured lens current has a wide aperture, and you can see a lot of light passing through the front glass of the lens straight through the back. If that hole were smaller, the aperture would be narrower and less light could pass through. Aperture isn't just a concept, but it's something you can actually see when you look at a lens.
You're not stuck with a single aperture. When a lens is rated a nice, wide aperture like f/1.8 that just designates its maximum. You can change the aperture on your camera to a narrower aperture to allow less light. Why would you do this? Narrower apertures provide a greater depth of field, meaning that more of the image will be in focus. When you're photographing a landscape, you want the entire image to be in focus and not just the part of the plane that your camera focused on. A higher, narrower aperture (f/12) provides that. A wider aperture (f/2.8) would make the landscape appear less sharp. That said, you don't always want everything in focus. When taking a portrait, for example, wide apertures are wonderful because you can focus on a person and allow the background to blur away. As demonstrated in the example photo to the above right, the only things in focus are the aperture blades of the lens. A wider aperture made this possible.
Put it All Together
Now that you understand focal length and aperture, you can read lens titles and know what they mean. Let's take the standard zoom lens you already have and break it down. Most likely it has a label of 18-55mm f/3.5-5.6. You know the first part, 18-55mm, means the lens can capture a view as wide as 18mm and zoom in as close as 55mm. You know the second part, f/3.5-5.6, means that the lens has a maximum aperture of f/3.5 when zoomed out to 18mm and f/5.6 when zoomed in to 55mm. But what does that mean in practical use? For that you need to understand what different types of lenses can do.
Types of Lenses
Lenses have various designations based on their focal length. Generally speaking, a lens with a very wide field of view exaggerates depth and one with a narrow field of view flattens depth. Changing focal lengths, whether that's by using a zoom lens or changing between different primes, allows you to achieve different affects with your photos. In this section we'll discuss the common categories of lenses and what you can do with them.
Note: Each lens category will contain a range of focal lengths. If you own a standard DSLR camera, it likely has an APS-C sensor inside. APS-C sensors magnify focal lengths by approximately 1.6 times. That means a 50mm lens essentially becomes an 80mm lens (as 50 x 1.6 = 80). This is important because this magnification can potentially make a lens in one category into a lens in another category. Bear this in mind when shopping, unless you know your camera has a full-frame (35mm equivalent) sensor and the 1.6x magnification doesn't apply to you.
Fisheye (12mm or less)
Fisheye lenses are the widest lenses you can buy. As pictured to the right, sometimes they're so wide that your image looks like a circle and your camera actually captures part of the inside of the lens barrel too. Fisheye lenses are used when you need to photograph absolutely everything possible in the frame or you want the look of extremely exaggerated depth. When you look at fisheye photos, you'll often find lots of pets and people staring directly into the camera because it makes their faces look funny. Of course, more practical uses include photographing small spaces or distorting reality to create a specific meaning in your image. If you want to see an example of a fisheye effect in real life, just look through a peephole in a door.
Wide Angle (18-30mm)
Wide-angle lenses create exaggerated depth just like fisheyes do, but to a lesser extent. When you want to capture a lot in your photo, you need to go wide. A wide angle cause some distortion, however. For example, if you were photographing a ladder laid horizontally across the frame, it would appear to curve. The photo to the right demonstrates this effect. Look at how the walls curve inward as you look at the image from bottom to top. (The inward angle occurs in part because of the low perspective, but the curvature is a distortion resulting from the wide angle lens.) Although some very expensive wide-angle lenses attempt to correct this distortion somewhat, and you can use post-production tools like Photoshop to make those corrections as well, the effect isn't necessarily bad. When you use a wide-angle lens, simply know the image will distort and the depth will be exaggerated so you can use it to your advantage.
Standard lenses mirror what the human eye sees most closely. If you want your photos to look natural, standard is the way to go. A 50mm lens is generally considered to be the closest to what the human eye sees, although some will argue a 35mm is closer. Regardless, both produce beautiful, natural-looking photographs. Additionally, 35mm, 50mm and 85mm are common focal lengths for inexpensive prime lenses (especially 50mm). This is great because it's a way to find lenses with wide maximum apertures (f/1.4, f/1.8, f/2 and f/2.8) without spending a lot of money. If you're looking to take portraits or close-ups of nature, a 50mm offers the most options. Many prefer 85mm for portraits, however, as it flattens the depth of the image even more (and depth isn't particularly flattering to the human face -- just look what a fisheye lens does and you can see). Regardless of what you choose, everyone should have a lens in the standard range. While they may not offer special features, they're rarely a bad choice for most types of photos.
When you're unable to get closer to the object physically, you pick up a telephoto lens. While you have the great advantage of getting closer to your subject without physically moving, telephoto lenses flatten depth to the point where it may look a little unrealistic. Consider this example: if you photographed two people walking towards you and one was many metres behind the other, a telephoto lens could make it look like both people were almost next to each other. Flattened space isn't necessarily a bad thing, but it's important to know a telephoto lens causes it so you can take that into account before using one. As you can see in the example to the right, telephotos can isolate single subjects beautifully even when they're far away. If you choose a telephoto lens, make sure to spend the extra money and get one with optical stabilisation. Everything is magnified by a telephoto lens, including the small movements of your hands and body when holding the camera. You'll end up with a lot of motion blur if the camera isn't stabilised, and since you won't have a tripod with you at all times, you can save yourself some ruined images if the lens can help stabilise itself.
Super Telephoto (300mm or more)
Super-telephoto lenses can shoot the moon. When you want to photograph something that's really far off, this is the type of lens you need. Super-telephoto lenses have the same pros and cons of regular telephoto but to more of an extreme. If you're not aiming as far away as the stars, you can achieve some cool effects such as those seen in the example to the right. The background is essentially obliterated and reduced to an incredibly smooth blur. Because telephoto lenses flatten space more than any other type, you can achieve beautiful selective focus in your images.
Special Types of Lenses
Some lenses offer additional features on top of their focal length that can create interesting effects. Macro lenses allow you to focus on an object that's incredibly close -- often closer than the human eye can see. Tilt-shift lenses selectively focus on an area of the image and create a miniaturisation effect. These two types are the most popular, but you'll find more if you start exploring. For example, Lens Baby offers its own brand of selective focus lenses that can create blur in parts of the image that a standard lens cannot achieve.
Special lenses can be a lot of fun, but since you're just starting out, you'll probably want to avoid them. They not only add more cost but more complexity to the process of capturing an image. When you're purchasing lenses, start with the basics. Once you have more control over a regular lens, you'll be able to do more with a lens that has a special feature (or two). If you want to learn more about the basics of photography, you should also check out our night school course. There's a lot to learn, but you can pick it up quickly if you keep practising. The great thing about photography is that you can do it almost anywhere. Enjoy whatever new lens (or lenses) you choose and have fun testing their possibilities.