Camera lens

Interchangeable Canon and Nikon lenses

Sigma lenses for cameras of different systems

A camera lens is an optical device that forms an image on the light-sensitive surface of a camera, video camera, or another instrument. In photography, the lens gathers light from the scene, focuses it on the image sensor or film, and strongly affects the angle of view, perspective, sharpness, lens speed, and the character of background blur.

In a broader sense, lenses are used not only in still cameras, but also in video cameras, microscopes, telescopes, binoculars, and other optical systems. This article is mainly about photographic lenses, meaning lenses for digital and film cameras.

Purpose and construction

The main purpose of a lens is to form a sufficiently sharp and correctly illuminated image on the camera sensor. To do this, a lens uses a group of glass or optical elements, and in some cases mirror or hybrid optical schemes. A modern photographic lens usually includes:

• optical elements that form the image;
• an aperture that regulates the amount of light passing through the lens;
• a focusing mechanism;
• a bayonet mount or another attachment system for connecting the lens to the camera;
• electronic contacts for data exchange with the camera;
• in some models, image stabilization, an autofocus motor, control rings, and mode switches.

A lens influences not only the technical quality of a photograph, but also its visual character. For the same subject, different lenses can produce different perspective, depth of field, background blur, geometric distortion, and rendering of fine detail.

Fixed and interchangeable lenses

Photographic lenses can be divided into two broad groups:

• fixed lenses are built into the camera and cannot be replaced by the user. Such lenses are used in smartphones, compact cameras, action cameras, and some video cameras;
• interchangeable lenses are mounted on a camera by means of a bayonet mount and can be replaced according to the task. They are used in DSLR and mirrorless system cameras.

Interchangeable lenses give the photographer more flexibility: the same camera body can be used with a wide-angle lens for landscapes, a fast portrait lens, a macro lens, or a telephoto lens for distant subjects.

Main characteristics

Focal length

Focal length is one of the main characteristics of a lens. It is expressed in millimetres and determines the image scale and angle of view. The shorter the focal length, the wider the angle of view; the longer it is, the more strongly the lens appears to bring distant subjects closer.

The size of the camera sensor must also be taken into account. The same lens gives a different angle of view on a full-frame camera and on a camera with a smaller sensor. For this reason, APS-C and Micro Four Thirds cameras often use the concept of equivalent focal length.

Approximate classification for a full-frame camera:

Lens type	Approximate focal length	Main use
Fisheye	8-15 mm	ultra-wide angle, creative distortion, panoramas, interiors
Ultra-wide-angle	14-24 mm	landscapes, architecture, interior photography
Wide-angle	24-35 mm	travel, street photography, reportage, general views
Standard	35-70 mm	everyday photography, environmental portraits, reportage
Short telephoto	70-135 mm	portraits, details, shooting from a moderate distance
Telephoto	135-300 mm	sport, wildlife, stage events, distant subjects
Super-telephoto	300 mm and longer	wildlife, aviation, sport at long distances

These boundaries are approximate: manufacturers and photographers may use slightly different classifications.

Angle of view

Angle of view describes how much of the scene is included in the frame. It depends on focal length and sensor size. For example, a 14 mm lens on a full-frame camera gives a very wide angle of view; Nikon lists a 114° angle of view on FX format for one of its 14 mm lenses.

As focal length increases, the angle of view becomes narrower. Therefore wide-angle lenses are useful in confined spaces and landscapes, while telephoto lenses are used for distant subjects and portraits with strong background blur.

Aperture and lens speed

Aperture is an adjustable opening inside the lens through which light passes to the camera sensor. Its size is indicated by an f-number, such as f/1.8, f/2.8, f/5.6, or f/11. The smaller the number after the letter f, the wider the aperture and the more light reaches the camera.

Lens speed is the maximum aperture of the lens. A lens with f/1.4, f/1.8, or f/2.8 is called a fast lens. It allows photography in low light and makes it possible to obtain shallow depth of field, where the subject is sharp and the background is strongly blurred.

A closed-down aperture, for example f/8 or f/11, increases depth of field: more objects in the frame remain sharp. This is often used in landscape and product photography.

Focusing and minimum focusing distance

Focusing is the adjustment of the lens for sharpness on a selected subject. It can be manual or automatic. Modern lenses often have built-in autofocus motors that differ in speed, precision, and noise level.

Minimum focusing distance shows how close the subject can be to the camera while the lens can still focus on it. For ordinary lenses this distance may be relatively long, while macro lenses are designed for much shorter distances and allow small objects to be photographed close up.

Image stabilization

Some lenses are equipped with optical image stabilization. Different manufacturers use different designations: for example, IS by Canon, VR by Nikon, OSS by Sony, and OIS by Fujifilm and Panasonic. A stabilizer compensates for small camera movements and helps obtain sharper handheld photographs, especially at slow shutter speeds and long focal lengths. Nikon describes VR technology as a way to reduce blur caused by camera shake.

Stabilization does not replace a short shutter speed when photographing fast-moving subjects: it helps against camera shake, but it does not freeze the movement of the subject itself.

Mount and compatibility

A lens mount is the mechanical and electronic connection system between the lens and the camera. Through the mount, the lens is fixed to the camera body, and the camera may control aperture, autofocus, stabilization, and transfer service data.

Each camera system uses its own mounts: Canon EF and RF, Nikon F and Z, Sony E, Fujifilm X, Micro Four Thirds, and others. When buying a lens, compatibility must be checked not only by brand, but also by the exact mount. For example, Canon states that EF lenses can be used on EOS R system cameras through an EF-EOS R mount adapter.

Adapters make it possible to use lenses from one system on another camera, but they can have limitations: autofocus, stabilization, data transfer, or automatic aperture control may not work in some combinations.

Types of lenses

Fisheye

A fisheye is an ultra-wide-angle lens with a very large angle of view, often around 180° or more. It produces strong geometric distortion: straight lines may bend, and space appears unusual. Such lenses are used for creative effects, panoramas, interior photography, and extreme sports.

Wide-angle lens

A wide-angle lens captures a large part of the surrounding space and is suitable for landscapes, architecture, interiors, reportage, and shooting in confined spaces. When used for people at close distance, it can noticeably distort proportions, so it is used carefully for classical portraits.

Standard lens

A standard lens gives an angle of view close to the natural perception of the scene. A classic example is a 50 mm lens on a full-frame camera. Standard lenses are suitable for everyday photography, reportage, portraits, and travel.

Macro lens

A macro lens is designed for close-up photography of small objects: insects, plants, details of objects, jewellery, and textures. True macro lenses often provide 1:1 magnification, when the object is projected onto the sensor at life size.

Telephoto lens

A telephoto lens is used for photographing distant subjects: animals, sports events, concerts, architectural details, and portraits with strong background blur. Such lenses have a narrow angle of view and visually compress perspective, reducing the apparent distance between objects at different depths.

All-purpose lens

An all-purpose lens covers a wide range of focal lengths, for example 24-105 mm, 18-135 mm, or 24-200 mm. It is convenient for travel and everyday photography when changing lenses often is undesirable. Its disadvantages may include lower lens speed or weaker image quality compared with specialized lenses.

Prime and zoom lenses

By construction, lenses are often divided into two types:

• prime lenses have one fixed focal length, for example 35 mm, 50 mm, or 85 mm. They are usually faster, lighter, and can provide very high image quality;
• zoom lenses allow the focal length to be changed, for example 24-70 mm or 70-200 mm. They are more convenient and versatile, but are often larger and more expensive when they have a high maximum aperture.

Image quality

The quality of a lens cannot be judged only by focal length or price. Several parameters affect the final image:

• sharpness — the ability to reproduce fine detail;
• contrast — the separation of subtle transitions between light and shadow;
• chromatic aberration — coloured fringes along the borders of high-contrast objects;
• distortion — geometric deformation, especially noticeable in architecture;
• vignetting — darkening of the corners of the frame;
• flare and ghosting — resistance to bright light sources in the frame;
• bokeh character — the appearance of background blur and out-of-focus highlights.

Many modern cameras and editing programs can automatically correct some optical defects, but the quality of the original optics remains important.

How to choose a lens

The choice of a lens depends on the task, budget, and camera. Before buying, it is worth considering:

• mount — the lens must be compatible with the camera;
• sensor size — full-frame, APS-C, or another format affects the angle of view;
• focal length — determines what subjects are convenient to photograph;
• lens speed — important for indoor photography, evening light, and background blur;
• stabilization — useful for video, telephoto lenses, and handheld shooting;
• weight and size — especially important when travelling;
• autofocus — critical for sport, children, animals, and video;
• price and availability — sometimes a simpler lens that is used more often is the better choice.

Approximate recommendations:

Task	Suitable lenses
Landscapes and architecture	wide-angle and ultra-wide-angle lenses
Portraits	50 mm, 85 mm, 70-200 mm, fast primes and zooms
Travel	all-purpose zooms such as 24-105 mm, 24-200 mm, 18-135 mm
Macro photography	macro lenses of 60-105 mm and longer
Sport and wildlife	telephoto lenses such as 70-200 mm, 100-400 mm, 150-600 mm
Video	lenses with quiet autofocus, stabilization, and a convenient focal-length range

For a beginner photographer, an all-purpose zoom or an inexpensive fast prime is often more useful than an expensive specialized lens. After gaining experience, it becomes clearer which focal lengths and features are actually missing.

Common mistakes when choosing a lens

• Buying a lens without checking compatibility with the camera.
• Looking only at the zoom ratio while ignoring lens speed and image quality.
• Buying a lens that is too heavy to carry comfortably.
• Expecting an expensive lens by itself to improve composition and lighting.
• Ignoring minimum focusing distance when photographing objects and details.
• Using a wide-angle lens for portraits from a very close distance, which can distort the face.

See also

• Camera
• Photography
• Aperture
• Focal length
• Lens mount