What is Camera Focal Length?
Camera focal length is the distance — measured in millimetres (mm) — between your camera's image sensor and the optical centre of the lens when the subject is in focus. It is the single most important number printed on any lens, because it determines two critical things: how wide or narrow your field of view is, and how much the lens magnifies your subject. A smaller mm number captures a wider scene, while a larger mm number zooms in closer. Whether you're shooting sweeping landscapes or distant wildlife, focal length is the spec that shapes every image you take.
It's easy to be a little daunted when it comes to choosing a lens for your camera. The different sizes, weight and numbers associated with camera lenses can become overwhelming. However, understanding lens focal length meaning and what it does will better help you decide the best lens for your type of photography. Here's a guide to focal length, explained simply.
Table of contents:
- How Does Focal Length Affect an Image?
- What is the focal length of a lens?
- Zoom vs. Prime lenses: which one is right for me?
- Lens Focal Length Comparison: How to choose the right focal length?
- Camera Lens MM Explained: What Do the Numbers Mean?
- Camera Focal Length Comparison: Visualising the Difference
How Does Focal Length Affect an Image?
Many beginners put a lot of thought into choosing the right camera body, but we are here to tell you, your camera lens has a huge influence on the quality of your photographs. Not only is a camera lens responsible for bending and shaping the light, but it also determines the field of view you'll see through the finder, and your image sensor will capture.
Before purchasing a lens, consider your photography goals and specific requirements:
- Lens Kit: Do you prefer a versatile single lens or a collection of specialised lenses?
- Weight: Is portability a priority?
- Subject Matter: What will you primarily photograph (portraits, macro, wildlife, architecture, landscapes)?
- Shooting Distance: Will you need to get close to your subject or capture distant scenes?
Understanding these factors will help you determine the ideal focal length for your needs. Our camera lens buying guide can assist you in selecting the perfect lens.
What is the focal length of a lens?
Put simply, the focal length of a lens is a measurement attributed in mm. Often people mistakenly think that this measurement refers to the physical length of the lens. It actually refers to the angle of view of the lens when focused to infinity. This dictates how magnified your subjects will be when using the lens and how far away from your subject you can be for optimum use.
A shorter focal length is presented by a smaller number, such as 16mm. This will provide you with a wider field of view more commonly used when you want to get more into your photographs, like landscapes for instance. A longer focal length, such as 400mm, provides a much narrower field of view and is used to zoom in on something such as an animal or a person or object far away.
Note: While they are often confused, focal length and focus distance are two different things. As stated, focal length is a characteristic of a lens which determines its field of view, while focus distance is simply the measurement between the focal plane of your camera and the subject you are focussing on.
Zoom vs. Prime lenses: which one is right for me?
There are two different types of lenses, regardless of their focal length; zoom lenses and prime lenses. With a zoom lens you can alter the focal length of your image! You may have seen a lens that extends or contracts when twisting it on the camera enabling the user to zoom out or zoom in on their subject. A 24-70mm zoom lens operates at 24 at its widest and at 70mm focal length at its most zoomed-in. It affords flexibility without having to change lenses, which makes it the best camera lens for travel, as you only need one zoom lens in your kit to cover all your bases.
A prime lens is like a fixed lens in that its focal length cannot be changed. You need to change lenses to adjust the focal length. Prime lenses most commonly come in the 35mm, 50mm and 85mm varieties. Prime lenses are not as versatile as zoom lenses but they usually provide superior optical and low-light performance, at a lower price point.
Lens Focal Length Comparison: How to choose the right focal length?
Sample Image Captured with a Wide Angle Lens
Wide-angle lenses
Wide-angle lenses are generally considered to be 35mm and below and afford a far greater field of view. These lenses are often thought of as having the best focal length for landscape photography, sought after by landscape photographers who can make use of getting more in the frame.
Standard lenses
Standard lenses sit around the 50-60mm range and are suitable for a variety of objects at mid-range distances such as portraiture. They provide a focal length similar to what the human eye sees.
Telephoto lenses
Telephoto lenses are longer lenses and offer a far greater capability to zoom in on a subject. 70-200mm range lenses are commonly used by portrait and event photographers, while they are also useful for sports and wildlife photography.
Super-telephoto lenses
Super-telephoto lenses are, as their name suggests, super-long telephoto lenses and often veer into 300mm and above. These lenses have the invaluable ability of getting you a tight crop of subjects that are considerably distant, which makes them perfect for professional sports and wildlife photography.
Sample Image Captured with a Telephoto Lens
Choose the best camera lens focal length for you
At Ted's Cameras, we have a wide range of resources to help you get started and ensure you're choosing the best camera gear for your needs. Read our beginner's guide to shooting in manual mode, and browse our range of camera lenses to get inspired. To get expert advice on all purchases, you can also visit your local Ted's Cameras store and speak to our expert staff.
Camera Lens MM Explained: What Do the Numbers Mean?
The millimetre (mm) value on a camera lens tells you its focal length. Here's a simple way to think about it:
- 14mm–35mm: Wide-angle. Captures a broad scene — great for landscapes and architecture.
- 35mm–70mm: Standard. Closest to natural human vision — ideal for street and travel photography.
- 70mm–200mm: Telephoto. Brings distant subjects closer — perfect for portraits and sport.
- 200mm–600mm+: Super-telephoto. Maximum reach for wildlife and action at distance.
On a crop-sensor camera, multiply the mm value by the crop factor (typically 1.5x or 1.6x) to find the 35mm full-frame equivalent focal length. This affects how your images look compared to a full-frame body.
Camera Focal Length Comparison: Visualising the Difference
Comparing focal lengths side by side is the fastest way to understand how dramatically your choice of lens changes a shot. Shot from the same position:
- 24mm captures a vast landscape with strong foreground depth.
- 50mm produces a natural, balanced perspective similar to the human eye.
- 85mm delivers flattering portrait compression with pleasing background blur.
- 200mm dramatically compresses background and subject distance — ideal for wildlife or sports.
- 300mm brings faraway subjects close with significant background compression.
When comparing lenses, always consider your shooting distance. A 200mm lens at 10 metres and a 50mm lens at 2.5 metres can frame a subject similarly, but the background and depth-of-field rendering will look entirely different.