Camera Lenses Explained
This guide to camera lenses explains the most important features of a lens, including lens mount, compatibility, focal length aperture, stabilisation and more.
One of the most daunting aspects of moving up from a smartphone, compact camera or bridge camera to a DSLR or mirrorless system camera is dealing with interchangeable lenses. Even experienced photographers can find the vast array of camera lenses confusing. This guide to the most important features of camera lenses should help make choosing the right one easier.
Most camera manufacturers use lens mounts that are specific to their cameras, but Micro Four Third and L-mounts are shared between a few manufacturers.
What is a Lens Mount?
The most important thing to know about camera lenses is that they have a specific mount, so they can only be used with certain cameras. Third-party manufacturers like Sigma, Tamron, Tokina, and Zeiss make lenses with mounts to fit a range of cameras, but Canon, for example, only makes lenses to fit Canon cameras, and Nikon only makes lenses that fit Nikon cameras.
The picture is a little more complicated because some lenses are designed for specific camera ranges. Canon EF-S mount lenses, for instance, are designed for APS-C format Canon DSLR cameras and cannot be used on full-frame DSLRs. Meanwhile, Canon EF mount lenses are for full-frame Canon DSLRs, but they can be used used on Canon's APS-C format DSLRs.
Canon also has two lens lines for its mirrorless cameras, RF and RF-S. RF-S lenses are designed for the company's APS-C format mirrorless cameras but they can be mounted on its full-frame mirrorless cameras as well. Canon RF mount lenses are designed for use on its full-frame mirrorless cameras, but they can be used on its APS-C format cameras as well.
It's important to note that the image you get from a lens will look different depending upon whether it's mounted on a full-frame or APS-C format camera. In some cases, a lenses designed for use on an APS-C format camera can be used on a full-frame camera but the camera will crop the image to APS-C format size (or it will show heavy corner shading). More on this later.
Here's a breakdown of which current lens mount is used by each camera manufacturer. The first camera type listed for each mount indicates the primary target for the mount.
Canon
Canon EF: Canon full-frame and APS-C DSLRs
Canon EF-S: Canon APS-C DSLRs
Canon RF: Canon full-frame and APS-C mirrorless cameras
Canon RF-S: Canon APS-C and full-frame mirrorless cameras
Fujifilm
Fujifilm X: Fujifilm X-series APS-C format mirrorless cameras
Fujifilm G: Fujifilm GFX medium format cameras
Hasselblad
Hasselblad XCD: Hasselblad medium format mirrorless cameras
Leica
Leica M: Leica M-series rangefinder cameras
L: Leica full-frame and APS-C format mirrorless cameras
Leica S: Leica medium format DSLRs
Leica SL: Leica full-frame mirrorless cameras
OM Digital Solutions (formerly Olympus)
Micro Four Thirds: Olympus and OM System Micro Four Thirds Cameras
Panasonic
Micro Four Thirds: Panasonic Lumix Micro Four Thirds mirrorless cameras
L: Panasonic Lumia full-frame mirrorless cameras
Pentax
Pentax K: Pentax full-frame and APS-C format DSLRs
Pentax K (DA): Pentax K-mount lenses that are designed its APS-C format DSLRs
Nikon
Nikon F (FX): Nikon full-frame and APS-C format DSLRs
Nikon F (DX): Nikon APS-C and full-frame DSLRs
Nikon Z (FX): Nikon full-frame and APS-C format mirrorless camera
Nikon Z (DX): Nikon APS-C and full-frame mirrorless cameras
Sigma
L: Sigma fp series full-frame mirrorless cameras
Sony
Sony FE: Sony full-frame and APS-C format mirrorless cameras
Sony E: Sony APS-C and full-frame format mirrorless cameras
Leica, Panasonic and Sigma all produce cameras with the L-mount and you can use any L-mount lens on any L-mount camera. Similarly, OM Digital Solutions and Panasonic manufactures cameras with the Micro Four Thirds (MFT) mount and any MFT lens can be used on any MFT camera.
Wide-angle lenses such as the Fujifilm XF 10-24mm F4 R OIS WR seen here tend to be shorter than telephoto lenses.
What is Lens Focal Length?
A lens’s focal length is the distance in millimetres between its optical centre when it is focused on infinity and the sensor or film inside the camera. The optical centre of a modern lens isn’t easy to identify because the barrel conceals several lens elements.
However, although there are few exceptions, short focal length lenses are generally shorter in length than long focal length lenses.
On a full-frame camera a lens with a focal length of less than 50mm is usually referred to as a 'wide-angle' lens while a lens with a focal length longer than 50mm may be called a 'telephoto' lenses. However, lenses with focal lengths around the 40-55mm range are often referred to as 'standard' or 'normal' lenses because they produce images with framing that's close to what we see with our eyes.
The Nikon Nikkor Z 180-600mm F/5.6-6.3 VR is a telephoto zoom lens with a focal length range of 180-600mm and a variable maximum aperture of F/5.6 (at the 180mm end) to F/6.3 (at the 600mm end). It’s designed for use on Nikon’s full-frame mirrorless cameras.
What is Angle of View in Photography?
A lens’ angle of view measures the extent of a scene it can project onto a camera’s sensor. A wide-angle lens is so-called because it captures a wide view of a scene (i.e., all or most of it) and has a large angle of view.
A lens’ angle of view can be measured horizontally, vertically, and diagonally. The Canon RF 24mm F1.8 Macro IS STM lens, for example, has a horizontal angle of view of 44 degrees, a vertical angle of view of 53 degrees, and a diagonal angle of view of 44 degrees. In comparison, the RF 400mm f/2.8L IS USM's angle of view measurements are 5 degrees 10 minutes, 3 degrees 30 minutes, and 6 degrees 10 minutes, which are much narrower.
Wide-angle lenses are popular for shooting landscapes because they enable you to capture an expansive vista, and telephoto lenses are useful for picking out distant details or tight framing of action.
This Nikon Nikkor Z MC 50mm F2.8 is a prime lens. As it produces framing similar to the human eye, 50mm lenses are often called ‘standard’ or ‘normal’ lenses.
What's the Difference Between Prime and Zoom Lenses?
Prime lenses have a single focal length, while zoom lenses allow you to change focal length to get a wider or narrower view.
Zoom lenses are very popular because of their convenience, but prime lenses generally produce better image quality than a zoom lens of a similar price. That said developments in optical design mean that zoom lenses are increasingly close to matching prime lenses for image quality.
Prime lenses often has a wider maximum aperture than a zoom lens covering the same focal length range. That's useful because it means you can use faster shutter speeds and blur the background more with the prime lens.
Because they only cover one focal length prime lenses are often smaller and lighter than a comparable zoom lens covering the same focal length.
The Nikon Nikkor z 600mm F4 TC VR S is a prime lens with a difference. The TC indicates that it has a teleconverter built-in and that can be applied with the flick of a lever. When the teleconverter is in action, the lens’ focal length switches from 600mm to 840mm. That type of technology does not come cheap.
What is Focal Length Magnification?
Focal length is a physical measurement, but the image framing that a lens produces depends upon the size of the sensor in the camera it is mounted on. That's because the lens needs to produce an image circle that's big enough to cover the sensor inside the camera it's mounted on.
For example, a full-frame lens is designed to project an image across a sensor that's the same size as a 35mm film frame. If this lens is then mounted on an APS-C format camera, the smaller sensor only occupies a part of the image produced by the lens.
As a result, the image captured by the camera looks cropped compared to the image captured using the same lens on a full-frame camera, or like a longer focal length lens has been used.
The focal length magnification (also known as a ‘crop factor’) describes the increase in effective focal length that the sensor produces.
Nikon, Sony, and Fujifilm APS-C format cameras have a focal length magnification factor of 1.5x, which means that a 50mm lens produces images comparable to a 75mm lens on a full-frame camera. Canon APS-C format cameras have a 1.6x magnification which makes a 50mm lens look like an 80mm optic.
Micro Four Thirds cameras have a sensor that's smaller than an APS-C format sensor and as result, Micro Four Thirds camera give a 2x focal length magnification factor. Consequently, as 50mm lens produces an image that's comparable with a 100mm lens on a full-frame camera. This makes Micro Four Thirds cameras attractive to anyone wanting a light camera system, especially if they are keen on wildlife photography and in need of long telephoto lenses.
While lenses are marked with their actual focal length, photographer often refer to their 'effective' focal length which is the focal length with the crop factor applied.
The iris blades inside a lens close to form an aperture through which light passes. The size of the aperture determines how much light passes through the lens to the film or sensor.
What is a Lens's Aperture
Lenses have an iris that can open and close inside their barrel to control how much light can reach the camera’s sensor. The iris comprises a series of blades, and the more blades there are, the more rounded the iris hole or aperture.
Aperture value is calculated by dividing the focal length (f) by the aperture diameter in millimetres. As a result, an aperture of f/1.8 is larger than an aperture of f/2.8, and f/2.8 is larger than f/5.6 etc.
While this convention of using fractions to describe aperture settings (or sizes) can be confusing at first, it means that any given aperture lets in the same amount of light, whatever lens it is set on. For instance, f/8 on a 35mm lens lets in the same amount of light as f/8 on a 100mm lens.
What are Fast and Slow Lenses?
Lenses with a wide maximum aperture (e.g., f/1.8 or f/2.8) are called ‘fast’ because they let in lots of light and allow fast shutter speeds to be used.
The maximum aperture of many zoom lenses varies as its focal length is adjusted, but more expensive zooms have a fixed maximum aperture such as f/2.8 or f/4.
These lenses are generally more desirable because the exposure doesn’t alter as you zoom in or out, but they also tend to be bigger, heavier, and more expensive than zooms with variable maximum apertures.
Stabilisation
Some lenses have gyros inside that can detect movement and then a motor shifts an element (or group of elements) to compensate. This enables the camera to capture sharp images at shutter speeds that would normally result in blurred photographs. The possible reduction in shutter speed is measured in stops or exposure values (EV) and is commonly 3-4 EV.
Most manufacturers have started to introduce hybrid stabilisation systems that use in-body stabilisation as well as lens stabilisation to extend the range of movement compensation.
The ‘R’ in the name of the Fujifilm XF 10-24mm F4 R OIS WR indicates that it has a ring that can be used to adjust its aperture setting. When a lens doesn’t have an aperture ring, the setting is changed using a dial on the camera.
What do Lens Names Mean?
Lens names often seem like a long and confusing list of numbers and letters, but they are designed to spell out the lens focal length and maximum aperture along with some of the key technologies inside.
The Fujifilm XF 16-50mm F2.8-4.8 R LM WR, for example, has the Fujifilm X mount (for Fujifilm X-series APS-C format cameras) and is a zoom lens with a focal length range of 16mm to 50mm (effective focal length 24-75mm). It also has a variable maximum aperture that changes from f/2.8 at the wide-angle (16mm) end to f/4.8 at the longest (50mm) point.
In addition, the R indicates that it has an aperture ring, LM indicates that it has a linear motor to drive the autofocus, while 'WR' shows that it is weather-resistant. The list of letters varies depending on the manufacturer’s naming convention, but the features are often the same or similar.
If only one focal length is listed rather than a range, the lens is a prime lens. The Fujifilm XF 23mm F2 R WR, for example, is a 23mm prime lens. It has an effective focal length of 34.5 mm on Fujifilm's X-series cameras as they have an APS-C format sensor.
