What a camera lens does
A lens gathers light from a scene and focuses it into a sharp image on the camera’s sensor or film. It also decides how much of the scene fits in the frame, how much light reaches the sensor, and how blurred the background looks. Most of the character of a photograph comes from the lens as much as from the camera body.
Two numbers describe most lenses: focal length, given in millimetres, and maximum aperture, given as an f-number.
Focal length and angle of view
Focal length controls the angle of view. A short focal length sees a wide area, and a long focal length sees a narrow area and magnifies distant subjects.
As a rough guide on a full-frame camera:
- Under about 35mm is generally considered wide-angle.
- Around 40mm to 60mm is considered a standard lens, with a perspective often described as close to what we see.
- Roughly 70mm and above is telephoto.
Sensor size matters. On cameras with smaller sensors, the same lens shows a narrower view, so a 35mm lens on an APS-C body frames something close to a 50mm lens on full frame. Manufacturers often publish this as a crop factor, commonly about 1.5x for APS-C and 2x for Micro Four Thirds.
Aperture and maximum aperture
Aperture is the adjustable opening inside the lens. A low f-number such as f/1.8 means a wide opening: more light, a faster shutter speed in dim conditions, and a shallower depth of field. A higher f-number such as f/11 means a smaller opening: less light and more of the scene in focus. For a closer look at the controls on the lens itself, see camera lens settings.
A lens is often called fast when its maximum aperture is wide, for example f/1.4 or f/2.8. Fast lenses tend to be larger, heavier and more expensive.
Prime lenses vs zoom lenses
A prime lens has a single fixed focal length. A zoom lens covers a range, such as 24-70mm.
- Primes are usually lighter and often offer wider maximum apertures for the price. They also encourage you to move your feet to frame a shot.
- Zooms are more flexible, which is helpful when you cannot easily change position or swap lenses.
Neither is better in general. The right choice depends on how you shoot. The trade-off is explored further for trips in travel photography focal lengths.
Main types of camera lenses
- Wide-angle: Good for landscapes, architecture and interiors. Wide lenses can stretch objects near the edges of the frame.
- Standard: Versatile for everyday photography, including street work. See street photography with a 50mm lens.
- Short telephoto (roughly 85mm to 135mm): Popular for portraits because it allows comfortable working distance and background separation. See the best portrait lens.
- Long telephoto: Used for sports, wildlife (see choosing a lens for bird watching) and other distant subjects.
- Macro: Designed to focus very close, often reaching life-size (1:1) reproduction. Lighting small subjects is covered in macro photography lighting setup.
- Fisheye: An ultra-wide lens, often with a field of view around 180 degrees, that produces strong curved distortion for a deliberate creative effect.
- Tilt-shift: Lets you adjust perspective and the plane of focus, mainly used in architecture and product work.
Other features worth knowing
- Image stabilisation: Built into some lenses (labelled IS, VR, OSS and similar) to reduce the effect of camera shake at slower shutter speeds. It does not freeze a moving subject. The image stabilization guide goes deeper.
- Autofocus motor and focus ring: Quiet, fast autofocus matters for video, events and moving subjects.
- Mount: Lenses must match your camera’s mount, or use a suitable adapter. Check compatibility before you buy.
- Weather sealing and build: Useful if you shoot outdoors in poor conditions, though not essential for everyone.
How to choose a lens
- Decide what you shoot most. Landscapes, portraits, travel and events each favour different focal lengths.
- Check the mount and sensor size of your camera.
- Consider the maximum aperture you need for low light or background blur, and balance it against weight and budget.
- Choose between a flexible zoom and a smaller, simpler prime.
- Look for independent reviews and sample images for the specific lens, since sharpness and autofocus vary between models.
A single standard zoom or a 35mm or 50mm prime covers a surprising range of work, so you can add specialist lenses later.
Where to go next
For wedding work, where reliability and range matter, see the best lenses for wedding photography. To understand the controls on a lens barrel, read camera lens settings.