Basic Photography 101: Understanding Focal Length in Camera Lenses

Focal length is the distance (measured in millimeters) between the point of convergence of your lens and the sensor or film recording the image. The focal length of your film or digital camera lens dictates how much of the scene your camera will be able to capture. Smaller numbers have a wider angle of view and show more of the scene, while larger numbers have a narrower angle of view and show less.

Focal length impacts the look and quality of a photograph in several ways:

• Field of view. Focal length determines how much of a scene is captured in an image. Shorter focal length lenses are called wide-angle lenses because they allow you to get a wider field of view in one image. Lenses with long focal lengths are called telephoto lenses, and have a smaller field of view.
• Depth of field. Lenses with long focal lengths tend to have a shallow depth of field, which means they can focus in on small objects (even faraway ones) at specific distances. Meanwhile, lenses with short focal lengths have a larger depth of field, which enables them to get a wider range of elements in focus.
• Perspective. Focal length can also change the perspective and scale of your images. A lens with a shorter focal length “expands” perspective, giving the appearance of more space between the elements in your photo. Meanwhile, telephoto lenses tend to stack elements in the frame together to “compress” perspective.
• Image shake. Image shake is the blurriness and reduction in image quality that occurs from the vibration of pressing down the shutter release. When using a lens with a long focal length and tight perspective, your lens and camera are more sensitive to the slightest motion. Image shake can be prevented by using a tripod.

There is a wide variety of camera lenses, and therefore different focal lengths, available to budding photographers. Certain lenses are better suited to certain types of photography; for example, ultra-wide angles are great for landscape photography whereas telephotos are a better option for wildlife photography.

• Ultra wide angle (focal length 8mm to 24mm): These lenses are sometimes called fisheye lenses, which have a very wide viewing area. While they can take an image of up to 180 degrees around the lens, they distort the image quite significantly, making everything appear almost as if inside a sphere.
• Standard wide angle (focal length 24mm to 35mm): Smaller focal lengths and a wider angle can distort images. With a lens of this size, distortion is minimal and the image appears more natural. Pretty much everything is in focus unless your subject is very close to the camera and there is less spatial distortion than a very wide lens, but it still makes things seem farther away than they actually are.
• Standard lens (focal length 35mm to 70mm): These versatile lenses are good for just about any type of photography, from portraits to landscapes. These all-in-one lenses render images roughly the way the human eye sees the world, and easily adjust to a shallow or deep depth of field, depending on aperture.
• Telephoto lens (focal lengths 70mm to 300mm or more): These lenses are ideal for picking out a distant subject, the way a telescope does. Good for compressing your subject and the background, which makes the background appear much closer to the subject. Telephoto lenses quite often have a shallow depth of field unless everything you’re shooting is far away.

Crop factor is a photography term for the difference between your camera's sensor size and a traditional 35mm film frame. Crop factor affects your focal length because a “cropped” sensor captures less of the projected image than a “full frame” sensor, resulting in a photo that appears more zoomed in. For instance, some camera brands, including Canon and Nikon, make DSLR cameras with sensors smaller than 35mm. Nikon’s DX cameras have a crop factor of 1.5, which means they’re only 75% the size of a traditional film frame.

Cameras with higher crop factors produce a narrower field of view that can create the impression of a longer focal length, even if you’re using a lens with the proper focal length for your subject. To avoid taking photos that feel too zoomed in, multiply the focal length of any lens you plan to use by the crop factor of your camera sensor, then use the resulting number (your effective or equivalent focal length) to make any adjustments to your equipment.

Using a telephoto lens for portraits would be as awkward as trying to photograph a hippo from afar, using only a fixed ultra-wide angle. Make sure you’re clear on what you’re photographing before jumping in and purchasing a new lens. Check this handy guide to camera lenses that will give you the right focal length for every subject.

• Best beginner camera lens. The 50mm is by far the most popular starter lens, as it strikes a nice balance between field of view and depth of field, and doesn’t require any tinkering with focal length to produce a crisp image. Learn more about different types of camera lenses here.
• Best lens for travel photography. Travel photography is unique in that you’ll want to travel light, but have the option of capturing a lot of detail. A standard zoom lens allows you to adjust your focal length, giving you enough flexibility to get each shot. Learn more about travel photography in our comprehensive guide here.
• Best lens for sports photography. Telephoto zoom lenses offer longer focal lengths that are ideal for capturing action-packed scenes from afar. Learn more about sports photography here.
• Best lens for landscape photography. Before heading out on an outdoor adventure, consider grabbing two lenses: a wide-angle (or ultra wide-angle), as well as a standard lens. With landscape photography, you want to have the flexibility to capture both scale and detail. Learn more about landscape photography here.
• Best lens for portrait photography. Fixed lenses (also known as prime lenses) with focal lengths between 35mm and 70mm make great portrait lenses. The lack of zoom options on a fixed lens ensures clarity of image for portraits (so no fuzzy or blurry faces). Learn more about portrait photography here.
• Best lens for macro photography. A telephoto lens of at least 200mm is best for macro photography. The focal length of this powerful lens can capture subtle details from afar. Learn more about macro photography in our complete guide here.
• Best lens for architecture photography. A standard wide angle lens features a decent field of view to capture most, if not all, of a building or cityscape.
• Best lens for street photography. As with portrait photography, street photography benefits from the unique, clear look that standard fixed lenses produce. If you want to get creative, however, opt for a standard zoom lens and use focal lengths to play with your subject’s size in relation to the background. Learn some basic street photography tips for beginners here.
• Best lens for wildlife photography. Telephoto zoom lenses come in handy for potentially dangerous situations, or scenarios in which you want to capture a scene without disturbing the subjects. Wildlife can be unpredictable, and a telephoto lens with a long focal length helps ensure you can keep enough distance between yourself and wildlife while still getting the shot. Read our tips for capturing better wildlife photography here.

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