Camera Lenses 101: What to know before you buy your first lens
posted Friday, December 2, 2016 at 3:29 PM EDT
Apertures, focal lengths, ƒ-stops -- with all the terms surrounding camera lenses, it’s completely normal for a new photographer with an interchangeable-lens camera to feel out of their depth of field and lost in a circle of confusion.
But have no fear, the purpose of this article is to give you an overview of camera lenses -- the terms you need to know, how they do the special things they do, and in particular, how they can be relevant to the kinds of photographs you want to make.
At the most basic level, it’s worth understanding that for all their bells and whistles, the purpose of a lens is to focus the light from a scene and direct it towards the sensor in your camera. There’s a lot of technology inside a lens that affects how it does this, but ultimately, all lenses achieve the same goal.
Not all lenses are created equal
Lenses that even appear to be similar in their names can offer dramatically different capabilities. For example, a lens with image stabilization built-in will help counteract the shakiness that just holding the camera with your hands can induce, but it can make a lens more costly. A lens might have special macro functions that help with taking very close-up pictures. You’ll have to decide whether these functions are worth the extra cost.
- This is the part of the lens that attaches to the camera, using a mount designed to fit a specific brand of camera. Generally, one manufacturers’ lens won’t fit on a camera designed by another manufacturer.
- These switches allow you to activate, deactivate, or otherwise alter features offered by the lens. For example, one of the switches on the above Fujinon lens allows you to activate or deactivate autofocus.
- Once a standard part of any camera lens, the aperture ring is growing more and more uncommon on modern lenses. The ring allows you to manually control the amount of light hitting the sensor by opening and closing the aperture of the lens. All modern cameras allow you to do this by selecting the aperture you want from the camera’s interface.
- Not all camera lenses have this function, which allows you to adjust the focal length of the lens -- these lenses are called “zoom lenses” because they allow you to “zoom in” from a wide angle scene, getting closer to your subject.
- You use this ring to adjust what is in focus for the camera. Most all modern cameras offer the ability to focus for you automatically, but in some cases, the camera can fail at this. For example, if it’s a dark scene, there might not be enough light for the camera to autofocus, but more than enough for you to figure out what should be in focus.
- You can use this part of the lens to attach a lens hood, which stops stray light from entering the lens and causing flare. Most modern lenses use this bayonet mount design for lens hoods, though there are a few other attachment methods.
- Attaching a protective cap to the front of the lens is a great way to prevent damage to the sensitive front glass element. Also, there is usually a threaded ring near the front of the lens, onto which you can attach filters for a variety of functional and aesthetic effects.
- For some zoom lenses, over time, the zooming mechanism can get a little loose, meaning that when the camera is pointed down, the lens can zoom on its own. Using a zoom lock switch will prevent this.
- This part of the lens is used to attach longer lenses to a tripod, to balance the camera-lens combination more safely. If you attached this long Fuji lens, for example, on a tripod just from the camera, there would be a lot of stress placed on the camera's lens mount.
- This part of the lens can rotate, allowing you to turn a camera while it’s attached to a tripod.
What is Focal Length?
Roughly stated, focal length refers to the amount of the scene that a lens captures. You would use a wide-angle lens to capture more of a scene, like what you would see in a landscape; a telephoto lens capture less of a scene, but magnify subjects farther away, bringing them closer. Focal length is measured in millimeters, but this doesn’t relate to the length of the lens. All you need to remember is that the longer the focal length, the narrower the angle of view and the higher the magnification. The shorter the focal length, the wider the angle of view and the lower the magnification.
For example, an 18mm lens is very much a wide-angle lens, while a 300mm lens would bring the scene much closer to you.
You probably received your camera with a kit lens, with focal length ranges typically spanning moderate wide-angle to short telephoto. You’ll probably be looking to buy a lens that corresponds to your shooting: If you've found yourself wishing you could see more of a scene, you may want to consider a wide-angle lens. If you frequently wish you could zoom in to see close-up shots of faraway birds, wildlife, or your kids on a sports field, you’ll probably be interested in a telephoto lens.
All about apertures
The aperture is the part of the lens which determines how much light is allowed to pass through to the sensor. Between this, ISO and the camera’s shutter, you’ll be able to dictate how bright or dark your captured image will be. An aperture is rated in ƒ-stops, a definition of which is a bit beyond the scope of this article. All you really need to know is that a low ƒ-stop number, like ƒ/2.8, will let in more light than a high ƒ-stop number, like ƒ/11.
If that hasn’t confused you yet, it’s worth noting that the process of moving from a low ƒ-stop number to a high ƒ-stop number is called “stopping down.”
Some zoom lenses are equipped with a what’s called a variable aperture, which is a design compromise to reduce the size and weight of the lens, not to mention the price. What this means is that as the lens is zoomed in towards a longer focal length, the largest aperture size will decrease, allowing less light to enter the camera. For example, the Nikon 18-55mm ƒ/3.5-5.6 lens will offer an aperture of ƒ/3.5 at the 18mm focal length, and ƒ/5.6 at the 55mm focal length. By contrast, the Nikon 17-55mm ƒ/2.8 lens will offer a wide ƒ/2.8 aperture regardless of what focal length you select. You get the maximum amount of light possible in the latter lens, but it’s more expensive, as well as larger and heavier.
Usually, you’ll select the aperture you want to use on your camera, but some lenses feature a ring which will let you manually select what aperture will be selected.
Zoom lenses versus Prime lenses
We’ve already mentioned zoom lenses, which have adjustable focal lengths. Lenses that don't zoom are called 'prime' lenses: if you need to put more or less of a scene into your frame, you’ll need to change your position or change lenses altogether. Generally, prime lenses are less costly than zoom lenses, because they don’t have to be as complicated. Prime lenses also typically offer a larger maximum aperture setting than zoom lenses and can do so without being very large.
Up until the early 1980’s you were focusing a camera lens by yourself: automatic focus wasn’t really prominent until 1977, and even then, it was slow and inconsistent. Today, camera lenses can focus quickly, near-silently, and can accurately focus consistently, even in sub-optimal conditions. Many lenses aren’t really designed with manual focus in mind, with thin manual focus rings that don’t have a lot of fidelity for small adjustments. There are companies, however, offering lenses without automatic focus, but it will be up to you decide whether you need the feature.
Categories of lenses
There is a jungle of lenses out there, and the choice can appear to be overwhelming. Fortunately, the different lenses are created for different purposes and are generally divisible into four categories.
Wide Angle lenses
A lens that has a focal length of 24mm or less is generally considered to be a wide-angle lens. Wide-angle lenses capture more of the scene, which makes them ideal for so-called 'landscape' photography. Imagine a huge mountain vista, the wide open African Serengeti or a massive waterfall: A wide-angle lens is a good choice for all these shooting scenarios. Wide-angle lenses are also good choices when shooting indoors, particularly if you want to capture all of an indoor scene like a 200 year-old cathedral in Europe. Finally, wide-angle lenses are great for emphasizing a foreground subject: Shoot wide and get in close, and your subject will dominate the frame.
Wide-angle lenses come in two flavors: rectilinear and fisheye. A lens which uses a rectilinear design seeks to try and keep the proportion and perspective of a scene in a way that's accurate to reality. A fisheye lens doesn't attempt this, just allow the optic to warp what you see in whatever way in order to fit it into the scene.
A lens that falls in the range between 35mm and 60mm is generally thought of as a standard lens, because the pictures they take tend to match the way scenes look to our eyes. This range is the workhorse for most photographers, providing a natural perspective for lots of shooting scenarios.
A lens that is longer than 70mm is generally considered a telephoto lens. Telephotos lenses magnify the scene to bring objects closer to the photographer. Not only do telephoto lenses make faraway objects appear closer, but they also makes objects appear closer together. Because you can’t get onto the field with the other athletes, telephoto lenses are a must for photographing most sports.
Special Purposes lenses
The categories above encompass about 95% of all the lenses created, but even then, there are a few other, generally more expensive lenses which exist for specific purposes.
A lens with a focal length between 85mm and 135mm, with a fast aperture, is a popular choice to shoot portraits. Some portrait lenses come with special features to control out-of-focus elements in the photograph, as well. Ever wonder why that professional photo taken at your friend's wedding is more flattering than your latest selfie? The pro probably used a telephoto 'portrait' lens, rather than the wide-angle focal length used for your selfie.
A lens which is designed specifically to magnify objects nearby is referred to as a macro lens. Macro lenses come in a variety of focal lengths, but generally come equipped with special features to help with the precise focusing that's required in taking a good photograph of a small object. What makes a lens 'macro?' The most intuitive feature is the 'minimum focus distance,' which is the closest an object can be to the camera and still be in focus... any closer and things get blurry. A lens designed for working at macro distances may have special features like focus limiters and special focusing modes.
Macro lenses can be used for other types of photography, but are generally larger, heavier and more expensive than a similar lens not optimized for macro photography.
These special lenses allow a photographer to adjust the plane of focus in their scene. You might be interested in this kind of lens if you photograph a lot of buildings and are concerned about making the angles of the building run parallel to the side of the image. As well, you can create a “miniature” effect which blurs the top and bottom parts of an image, as shown in the example below.
Special Lens Technologies
Some lenses offer more features than others, generally making them more expensive, but also provide a better or more sophisticated shooting experience for the photographer. Different manufacturers have different names for some of these technologies, but generally, they all boil down to different ways of saying the same thing.
The most common technology making its way into lenses today is image stabilization. Holding a camera steady so that you can take a crisp, sharp photograph of a subject can be an art, especially if the camera and lens weigh several pounds. Image stabilization is a technology where one of the elements of a lens is gyroscopically stabilized, compensating for the hand-holding motion of the photographer.
Image stabilization used to be found only in the most expensive lenses, but improvements in the technology have seen it being implemented in even relatively economical ones as well. However, it’s worth noting that no amount of image stabilization will stop your subject from moving around.
Another technology of note is quiet autofocus. When digital cameras started being able to record movies, the sound of a lens focusing suddenly became an issue, as it was loud enough to be picked up by the microphone in the camera. All the manufacturers have become aware of this, and newer lenses now have more modern autofocus systems, which are both extremely quiet and can also support improved continuous autofocus, like you would find in a regular video camera.
Finally, some recent lenses also include features you'd normally see in a dedicated video camera, like power zoom. With this feature, the photographer is able to adjust the zoom of the lens smoothly and at a consistent speed: this kind of thing is great for movie-making.
We’ve covered a lot of ground in this article. There’s no such thing as a perfect lens, as they are all different in their own subtle ways. The most important thing is finding the lens or lenses that match your shooting style: often times a photographer doesn’t get the images they want because they’re not shooting with the right lens. Hopefully, this article has helped you get started to find exactly what you need!