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Choosing and Using a Lens for an SLR


Canon EF 24-105mm f/4L IS USM Lens

Investing in a new lens can help you broaden the type of pictures you take

For me, it started with the purchase of my first digital SLR camera. The kit came with one lens, which was fine and dandy for about two weeks. Then I decided to purchase another lens. But where would I start? And what in the world did those lens descriptions mean? It seemed there were infinite possibilities to choose from. And I needed to be sure that the lens I ended up with would work with my camera, and give me the type of pictures I wanted.

Choosing a lens can be a daunting task for all of the reasons mentioned above, so I pulled together some info from my own experiences, as well as those of other Crutchfield shutterbugs. In this article, we'll help you decode "lens speak." We'll also explain popular types of lenses and the types of photography where they excel.

Deciphering lens lingo

Reading the name of a lens can seem a bit like translating a different language. But once you know what each part means, you'll find that the name gives you lots of essential information.

Here are a couple examples that we've broken down:


The name of a lens will give you a lot of important info about the series, focal length, maximum aperture and image stabilization.

Compatibility: brand, series, and sensor size

Of course, you want to make sure any lens you choose will fit and work properly with your camera. If you're buying a Nikon lens for a Nikon camera, that's a pretty good indicator that you're on the right track. However, if you're buying a third-party lens, you'll want to be sure the lens is intended for your brand of camera.

After confirming the lens will work with your brand of SLR, the next step is seeing if the lens is compatible with your particular camera's model or series.

Different series or lines of digital SLRs, even within the same brand, can use different lens mounts. If you choose a lens that's not intended for your series of camera, it may not work at all, or you may lose functionality, like the ability to autofocus. For example, if you have a Nikon digital SLR camera like the D3100, you'll want to be sure you choose a lens that's listed as AF-S or AF-S DX to ensure full compatibility. You can generally find this info in your camera's owner's manual if you're not sure.

Another thing to consider is the image sensor in your camera. There are basically two different sensor sizes:

  1. "full frame" sensors, which are the same size as one frame of 35mm film, like those in traditional film SLRs; these are generally in higher-end cameras
  2. smaller image sensors, like those found in most digital SLR cameras

You'll want to keep your camera's sensor size in mind when you select a lens, because mismatching can give you undesirable effects. For example, a small-frame lens (DX models for Nikon and EF-S for Canon) on a full-frame camera may not work at all, and if it does, it may only let you capture photos at a reduced resolution.

On the other hand, you can usually use a full-frame sensor lens on a small-sensor camera, but your focal length will be subject to "crop factor." That is, a full-frame lens (intended for a camera with a larger sensor) will project a larger image circle than your image sensor can capture, so it'll appear as if you've zoomed in slightly on your subject. For more information on this complex topic, see the discussion in our digital camera glossary.

full frame vs. small frame

There are two main types of image sensors: full frame sensors, which are the same size as one frame of 35mm film, and small frame sensors which are found on most digital SLRs.

Focal length

The next info you'll see in a lens description is the focal length. It'll either be a single number or a range of numbers. A single number indicates that you're looking at a lens with a fixed focal length, sometimes called a "prime" lens. You won't be able to zoom in or out from your subject — you'll have to move closer or further away to change your magnification. A range of numbers reflects the minimum and maximum focal lengths on a zoom lens, which allows you to get closer or further from your subject without physically moving.

Lenses can be grouped into a few different categories based on focal length. We'll touch on those we've seen most often: wide-angle, telephoto, and macro.

A wide-angle lens captures a wider view of a scene than the human eye can see, with a focal length or range that's generally less than 35mm. This lens can be great for outdoor shooting when you want to give a sense of the vast size of a location — a sweeping mountain range or a towering skyscraper. You'll find a wide-angle lens is also useful when trying to get a group shot of a lot of people in a little room.

It's worth noting that wide-angle lenses aren't an optimum choice for portraiture. They produce potentially unflattering people shots because they may make people's faces appear stretched out. We'll get into the optimum focal length for flattering portraits a little later in the article.


Here are a couple photos of the same subject, taken at different focal lengths. An abbey photographed with my 18-55mm lens at 55mm (above) and then with my 55-200mm lens at 185mm (below).


A telephoto lens allows you to zoom in on or magnify subjects that are far away. These can be fixed focal length or zoom lenses. The zoom lenses allow you to select the magnification that's right for your subject or scene. You can adjust the focal length to capture candid photos of a birthday party in your yard or focus in on a single child. The higher the maximum focal length, the further away you'll be able to see.

A macro lens lets you get really close to your subject — most of the time mere inches away — but still get crisp and clear photos. It's designed for taking close-ups of flowers and other subjects where you'll really want to show the texture. Macro lenses usually come in fixed focal lengths, and can also be a great choice for shooting portraits or even everyday photography.


A macro lens is helpful for getting extreme close-ups that expose the details of your subject.


Aperture describes the size of the opening in a lens that determines the amount of light let into the camera, and it affects a number of different aspects of photography. It's measured in "f-stops." A higher f-stop number corresponds to a smaller opening, which admits less light. SLR lenses will typically show a single maximum f-stop like f/1.8 or a range of maximum f-stops like f/3.5-5.6. You'll commonly see a range of maximum apertures when you're looking at a zoom lens with a range of focal lengths, while prime lenses will have only one maximum f-stop number.


A lens at minimum aperture (left) lets in only a small amount of light, while a lens at maximum aperture (right) lets in the maximum amount of light possible.

Some lenses are described as being "fast." This relates directly to aperture — a lens with a large maximum aperture (indicated by a lower f-stop number) lets more light into the camera. By letting more light into the camera, you can shoot with faster shutter speeds in settings with less light, and your photos will still be properly exposed.

Faster shutter speeds help you "freeze" images of moving subjects more effectively. This makes a fast lens ideal for shooting indoor sports, a toddler's birthday party, and other events that feature rapidly moving action. Keep in mind, however, that fast lenses use larger, more costly glass elements that can result in added size, weight, and a higher price tag.

Bike in focus

Shot at f/2.8

The aperture setting also affects how much of your photo is in focus, also known as depth of field. For example, only the bike is in focus in the image above (taken at f/2.8), while both the bike and the background are in focus in the image below (taken at f/22). Lenses with a large maximum aperture give you more control over depth of field, an important aspect of creative photography.

Bike and background in focus

Shot at f/22

You may also see lenses where either the number of aperture blades or the shape of the aperture blades is described. The aperture opening is created by a series of blades that form a circular hole that lets light pass into the camera. The blades contract and expand to form smaller and larger holes, respectively.

The closer the shape of the hole is to a perfect circle, the better the resulting photos. Because of this, you may see manufacturers increase the number of aperture blades or use curved aperture blades on some high-quality lenses.

Image stabilization

If your camera doesn't have built-in image stabilization, you may want to invest in a lens that has its own image stabilization. You'll see this in the lens description with an IS or VR (indicating "image stabilization" or "vibration reduction," respectively). Image stabilization can be particularly important for telephoto lenses where handshake is magnified as you zoom in on a subject.

Describing the internal components of a lens

You may see information about the makeup of the lens itself — the number of lens elements, the shape of the lens elements, or the type of glass used in those elements. These build features can affect the overall quality of the image, so if you want to shoot extremely crisp, accurate, professional-quality photos, it's good to pay attention to them.

For example, you may see a lens that has aspherical lens elements. The aspherical shape allows the lens elements to be smaller, which also allows the overall lens to be smaller and lighter. It also results in photos where the focus is crystal clear across the entire field of the lens — from one edge to the other edge.

Low-dispersion glass is another indicator of quality. It minimizes "color fringing," where you may see different bands of color on the edge of subjects.

Other considerations when choosing a lens

Pay attention to the size and weight of the lens. While it may not be a deal-breaker if the lens you end up with is big and bulky, it'll influence the bag you choose to cart it around. And it'll certainly affect whether or not it becomes a lens you take on long hiking trips where backpack space is limited.

If your lens weighs more than your camera body, as is sometimes the case, you may end up attaching the tripod to the lens to keep the weight distribution balanced. Most heavier lenses come with a tripod ring, making it easy to secure the lens directly to the tripod.

Common shooting scenarios and the types of lenses we'd use

Below, we've outlined a few common shooting scenes and the lenses that we'd use in these scenarios. Remember to keep in mind that a variety of lenses could work in many situations, but these would be our ideal choices.

All-in-one for travel
If we are traveling and don't want to carry a heavy bag around with us, we'll probably choose a zoom lens that ranges from wide-angle (18-20mm) to telephoto (200-300mm). That'll give us the opportunity to shoot wide environmental shots as well as close-ups of distant objects without having to change lenses. Switching lenses in the field can be nerve-wracking as one tries to keep dust and dirt out of two different lenses as well as the camera body.

The most flattering focal range for portrait photography generally falls between 80 and 150mm, remembering to account for crop factor. For an artistically blurred background, choose a lens with a large maximum aperture, like a macro lens.

Landscapes and expansive outdoor shots
If we are trying to capture sweeping environmental shots, like a tropical beach, a monstrous skyscraper, or a snow-capped mountain range, we'll probably go with a wide-angle zoom lens. That way, we can frame the scene and record the scope of our subject.

For these types of shots, a UV filter will minimize haziness and glare, while a polarizing filter will increase contrast between colors. We'll cover filters in more detail later on in this article.

Nature photography
If we were shooting nature photography, we'd want a telephoto lens that would let us zoom in on distant wildlife. But we'd also want a lens with short minimum focal distance so we could snap macro shots right next to plant life.

Indoor photos
There's typically less light when shooting indoors, so we'd look for a lens with a large maximum aperture. That'd let us use a faster shutter speed and still get properly exposed photos. Here, a wide-angle lens will give you the ability to capture the entirety of a room and all the people within it whereas a lens with a higher focal length gives you better photographs of individuals.

Ideal for action
For action, we'd want a lens with telephoto capability, so we can get close to the action, even when it's occurring across the field. And ideally, a large maximum aperture combined with a tripod will let us really freeze the action of any sporting event.

Lens storage and care

Tamrac System 6 camera bag

A good camera bag will protect your camera bodies and extra lenses while keeping them accessible

Once you purchase a lens, you'll want to keep it at its best. And a good way to do that is to protect the lens while it's not in use. Keep it in a camera bag when it's not attached to your camera.

You can also invest in lens clothes and brushes to gently remove dust and minor debris from the front of the lens without scratching or otherwise damaging the glass.

It seems pretty obvious to keep the lens cap on the lens when it's not in use, but we know from experience that lens caps are really easy to misplace or lose all together. So here's one tip that we've used with success: purchase a little bit of Velcro® from a craft store, then attach one side of the Velcro to the outside of the lens cap, and the other side to the your camera body or the outside of a frequently used camera bag. This will give you a handy place to store your lens cap when you're shooting photos.

Expand your photography potential with filters and other extras

Polarizing filter

Filters offer protection for your lens and can give you a variety of photographic effects.

Filters, first and foremost, offer protection for the expensive glass lens. Some filters also add a variety of effects to your photographs.

While some effects can be reproduced using photo editing software, it's helpful to have the filter in the field with you so you can adjust your scene and filter to get the desired effect.

There are quite a few different types of filters. We'll give a brief overview of the most popular filters and what they'll do for your photographs.

A clear filter protects your lens from minor bumps and scratches. In fact, you can purchase a clear filter and keep it on a lens the entire time you use it. It won't protect your lens against major bumps or falls, but it's much less expensive to replace a filter that swings into the wall than to replace a lens. Because these filters are perfectly clear, they offer no optical effects.

UV and haze reduction
A UV filter absorbs UV light as you snap a picture and gives photos a gentle warming effect. A UV and haze filter also minimizes the haze that settles in the distance of landscape photos. One of these filters can help you capture crystal clear panoramic photographs.

Photo with polarizing filter

A polarizing filter is a good choice for outdoor photography — you'll get photos with increased contrast between blue skies and white clouds.

A polarizing filter is used in outdoor photography. It reduces reflections on non-metallic surfaces like water, ice, and glass. And it increases the contrast between colors, which makes backdrops seem to pop, like a bright blue sky with white clouds. A circular polarizing filter features an adjustable ring. Adjust the ring as you look through the viewfinder, then snap a photo when the sky looks like it's at its bluest point.

Lens hoods
These prevent sunlight from creating "flare" — streaks of light that appear in your pictures — and are sometimes included with lenses. Light at errant angles, especially from the side, can creep into photos and create flare by reflecting across the surface of the lens. Hoods minimize this effect by blocking light from sides of the lens, so your photos are only exposed with the light you want.

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