Lenses 101: An Essential Guide
March 18, 2019
Lenses are the eyes of any camera. They determine the distance from which you can focus on a subject, how much of it you can fit in frame and how quickly, brightly and sharply you can capture it. They can depict things faithfully or play optical tricks for artistic effect.
Camera lenses influence image quality to a greater degree than do camera bodies, which interchangeable lenses usually outlive. So if you’re yet to buy a camera, we recommend you decide on lenses first before buying into a particular camera system.
Which Lens Should I Buy?
Whether you’re buying a lens for your DSLR or mirrorless interchangeable lens camera or deciding on a compact camera based on the lens that it comes with, choosing a camera lens depends on multiple factors including what and how you shoot, which camera you shoot with, and how much you’re prepared to spend.
Here are some key things you’ll need to consider when looking to buy camera lenses:
Zoom or Prime?
Zoom Lenses
Zoom lenses can zoom anywhere between a specified focal length range (e.g. 24-70mm). Making a subject appear closer or further away is a simple matter of zooming the lens in or out respectively, as opposed to physically moving yourself relative to the subject. As such, they’re ideal for travel or general purpose, times when it’s difficult to get close to a subject, and situations in which you need to reframe quickly.
It’s possible to get superzooms that cover a very wide focal range (e.g. 18-300mm). While these lenses are extremely versatile and convenient, there’s a slight tradeoff between these benefits and image sharpness. Generally speaking, all else being equal, the greater a lens’ zoom range, the more that its optical quality tends to decline.
Zoom lens advantages (compared to prime/fixed focal length lenses):
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Versatile
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Convenient – less (if any) need to change the lens
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Allows you to keep your distance if required by practicality or safety
Zoom lens disadvantages (compared to prime/fixed focal length lenses):
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Not as sharp
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Not as fast/bright (see Maximum Aperture, below)
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Usually larger
Popular for:
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General use
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Travel
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Landscape
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Wildlife
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Sports & action
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Weddings & events
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Live music & performance
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Real estate
Prime Lenses
Prime lenses have fixed focal lengths (e.g. 85mm), meaning they can’t zoom in or out. Unlike zoom lenses, which are sort of all-rounders, primes are specialists—so they’re almost always sharper.
Primes also tend to have a wider maximum aperture (see below), which allows for better low light performance, faster shutter speeds, shallower depth of field and more pronounced bokeh (blurred background). This makes them especially favoured by portrait and street photographers.
Prime lens advantages (compared to zoom lenses):
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Sharper
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Better low light performance
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Let you shoot with faster shutter speeds
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Capable of shallower depth of field and more pronounced bokeh (blurred background)
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Usually smaller and sometimes lighter
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Focal length limitation encourages creativity
Prime lens disadvantages (compared to zoom lenses):
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Can’t zoom in or out – need to change the lens or physically move to change your focal length
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Not as versatile
Popular for:
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Portraiture
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Product photography
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Street photography
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Weddings
The Beauty of Choice
The beauty of interchangeable lenses is the option to use whichever lens your taste or intent dictates at the time. Most enthusiast photographers will, over time, acquire a selection of zoom and/or prime lenses to use for different purposes. So you might, for example, attach a 16-35mm zoom to capture a broad oceanscape at sunrise; use a wide-aperture 50mm prime to shoot scenes at night and/or portraits with soft backgrounds; or switch to a 24-105mm when you need to travel light but cover multiple bases.
Camera Compatibility & Sensor Size
In the case of interchangeable lens cameras, lenses are made to fit particular brands, series or formats of camera, so it’s important that your camera and lens/es are compatible. Mounting a lens on an incompatible camera (without an appropriate adapter) usually won’t work and can damage both devices.
It’s worth noting that micro four-thirds cameras from Panasonic and Olympus have the same lens mount, so their mirrorless lenses and cameras are interchangeable.
It’s usually possible to mount a full frame format lens on an APS-C format camera of the same brand (though it’s best to check with the manufacturer before attempting to). However, because full frame sensors are bigger than APS-C sensors, an image captured by a full frame lens on an APS-C sensor appears slightly ‘cropped’ or more zoomed in compared to an image captured by a full frame lens on a full frame sensor. This amount of crop corresponds with the size ratio between the two different sensors and is known as crop factor.
Sensor Size & Crop Factor
| Sensor Size | Sensor Dimensions | Crop Factor |
|---|---|---|
| Full frame / 35mm format | 36 x 24mm | 1x |
| APS-C (Fujifilm, Nikon, Sony) | 23.6 x 15.6mm | 1.5x |
| APS-C (Canon) | 22.2 x 14.8mm | 1.6x |
| Micro four-thirds | 18 × 13.5 mm | 2x |
Focal Length
In conjunction with a camera’s sensor size, the focal length of a lens (expressed in mm) determines how much of a scene (i.e. the angle or field of view) it captures. Shorter focal lengths give a wider field of view (ideal for landscapes) while longer focal lengths offer a narrower, more zoomed-in field of view (ideal for wildlife).
For ease of comparison, focal length measurements on all camera lenses (regardless of which sensor they’re designed for) are always relative to full frame format. This, along with crop factor, provides a standard reference by which to determine a lens’ angle of view on any camera.
The smaller a camera’s sensor compared to full frame format, the narrower the angle of view that any lens would capture on it compared to on full frame. So a 50mm lens (which gives a 50mm angle of view on a full frame sensor) would give a 50 x 1.5 = 75mm angle of view on a Nikon APS-C sensor or a 50 x 2 = 100mm angle of view on a micro four-thirds sensor. Because this only affects angle of view (and not actual focal length), it’s known as effective focal length.
For more information on camera sensors, check out our Beginner's Guide to Digital Cameras.
Lens Types & Effective Focal Lengths
| Lens Type | Sensor Format | |||
|---|---|---|---|---|
| Full Frame | APS-C (Fujifilm, Nikon, Sony) | APS-C (Canon) | Micro Four-Thirds | |
| Fish Eye | Up to 14mm | Up to 9mm | Up to 8.75mm | Up to 7mm |
| Wide Angle | 14-35mm | 9-23mm | 8.75-22mm | 7-18mm |
| Standard | 35-70mm | 23-47mm | 22-44mm | 18-35mm |
| Short Telephoto | 70-100mm | 47-67m | 44-63m | 35-50mm |
| Telephoto | 100-300mm | 67-200mm | 63-188mm | 50-150mm |
| Long Telephoto | 300mm+ | 200mm+ | 188mm+ | 150mm+ |
Fish Eye Lenses
With their extremely wide visual field, fish eye lenses capture hemispheric-looking images in which straight lines appear highly curved towards the edges. Fish eye lenses lend themselves well to underwater photography and very small spaces, e.g. phone booths (if distortion isn’t a concern), will as well as creative shots, particularly of cityscapes or highly geometric subjects.
Ideal for:
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Creative images
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Small spaces (if you don’t mind distortion)
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Underwater photography
Wide Angle Lenses
Wide angle lenses are the go-to for scenes or subjects that are too large or dramatic in scope for other kinds of lens. They can capture a small room in its entirety, do justice to a cathedral’s grandeur and show the scale of a landscape, city skyline or concert crowd.
Because wide angle lenses offer an angle of view that exceeds the human eye’s, they tend to have a distorting or ‘stretching’ effect (albeit less pronounced than in fish eye lenses), mainly towards the edge of the frame. The wider the lens, the greater the effect, though it’s more noticeable at focal lengths wider than around 24mm.
Ideal for:
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Architecture/interiors
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Astro photography
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Landscapes
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Travel
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Weddings (in conjunction with other lenses)
Standard Lenses
Standard lenses most closely resemble our natural visual field. Some of the most popular focal lengths for prime lenses (e.g. 35mm, 50mm) fall into this category because they work well for many different subjects: environmental and upper body portraits, street photography, and semi-wide angle snapshots.
Thanks to this versatility, standard focal length lenses are staple choices for the majority of photographers. They’re ideal for when you only want to carry one lens and/or aren’t sure what you’ll be shooting.
Ideal for:
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Events
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Lifestyle
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Portraits (environmental and upper body)
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Street photography
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Travel
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Weddings (in conjunction with other lenses)
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General purpose
Short Telephoto Lenses
Short telephoto lenses are ideal for portrait photography as they don’t distort facial features, which wider angle lenses can. This same property also makes them suitable for product photography. They also provide slightly more zoom than a standard lens, which can come in handy for travel.
Ideal for:
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Events (in conjunction with a wider lens)
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Lifestyle photography
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Portraiture
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Product photography
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Travel (in conjunction with a wider lens)
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Weddings (in conjunction with other lenses)
Telephoto Lenses
Telephoto lenses make subjects appear significantly closer. They’re often used by nature/wildlife and sports photographers but also handy for portraits, travel and shows/performances.
Ideal for:
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Action
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Portraiture
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Shows/performances
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Sports
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Travel (in conjunction with a wider lens)
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Wildlife
Long Telephoto Lenses
With the longest focal length of any lens, long telephoto lenses are the choice for serious wildlife and sports photographers. They allow you to take close-up shots even from a considerable distance. However, their size and weight make them difficult to hold steady or for long periods, so many photographers use a monopod to support them.
Ideal for:
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Action
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Sports
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Wildlife
Macro Lenses
Able to focus at very close distances, macro lenses are designed to capture small subject matter (such as flowers, insects or jewellery) up close and in detail. Their magnification factor (e.g. 0.3x, 0.5x or 1.0x) determines how large, relative to life size, the subject would appear on a full frame sensor. Full 1.0x magnification is ideal for true macro photography. A macro lens’ focal length meanwhile determines how close you need to be to a subject; the general rule of thumb is around 50mm for fauna and 100mm for flora.
Due to their focal length and (usually) wide maximum aperture, macro lenses can also serve as excellent portrait lenses. Most macro lenses have controls that allow you to switch between different focusing distances.
Ideal for:
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Creative images
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Flowers & insects
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Portraits
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Product photography
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Weddings (for small details)
Tilt Shift Lenses
Tilt shift lenses are specialised lenses that allow you to manipulate focus and perspective by tilting or shifting the focal plane so it’s not parallel to the image sensor. Tilt can create highly selective focus effects (as seen in pretend ‘miniatures’) while shift can simulate the look of shooting from a different position (higher/lower or to the left/right)—very useful for straightening verticals in architectural shots or shooting into mirrors.
Ideal for:
- Architecture
- ‘Miniature’ photography
- Shooting into mirrors
Lens Converters
Lens converters are a relatively affordable, simple and extremely compact way of extending a lens’ zoom or widening its field of view. Just bear in mind that they usually reduce a lens’ maximum aperture (by 1.4 stops in the case of 1.4x converters or 2 stops in the case of 2x converters) and can affect peripheral image quality to a small degree.
Maximum Aperture
A lens’ maximum aperture (denoted in f-stops, e.g. f/2.8, f2.8 or 1:2.8) indicates how wide a lens’ blades can open, which determines how much light gets through the lens. The smaller the f-stop number, the more light the lens can let through, enabling you to shoot in dimmer conditions and with faster shutter speeds.
In some zoom lenses, the maximum aperture reduces the more you zoom in. (So a lens with a maximum aperture of f/3.5-5.6 can open up to f/3.5 when fully zoomed out but can only open as wide as f/5.6 when fully zoomed in.) Higher grade zooms can maintain their maximum aperture regardless of your chosen focal length, giving you greater flexibility in all shooting conditions.
(For more information on aperture and how it affects exposure, please see Playing with Light: Exposure 101.)
Image stabilisation, vibration reduction, optical steady shot… Every camera lens manufacturer has a different name for it, but this feature (present in some lenses or—for some brands—cameras) has the same fundamental effect of reducing image blur caused by hand shake at slower shutter speeds. Uncommon in prime lenses (which can often be used at fast enough apertures to overcome camera shake), stabilisation allows you to shoot handheld several stops slower than would otherwise be ideal. It’s particularly helpful in lenses with longer focal lengths.
It should be noted that stabilisation won’t reduce motion blur from a moving subject. This can only be achieved by shooting at a faster shutter speed.
To shoot static subjects as sharply as possible, mounting your camera on a tripod is by far the best method. In this case you should turn stabilisation off to prevent the lens’ internal elements from shifting as the lens searches for movement to counteract.
Construction
The price of a lens is usually relative to the quality of its optics and build. More affordable lenses tend to be made from lighter weight materials like plastic and cheaper glass. More professional ones are usually constructed from metal and high-grade optical glass (which tend to make these lenses bigger and heavier but more durable) and are often weather sealed against dust and moisture.
Focusing
Most lenses will allow both autofocus and manual focus, though some may only allow one or the other. In most shooting scenarios autofocus tends to be easier and more accurate, though there are some situations (e.g. video, very busy/detailed scenes, very low/high contrast) in which manual focus often works better.
The focus motor that drives a lens’ autofocus can significantly affect the noise and speed of the lens’ operation. Ultrasonic (aka supersonic, hypersonic or Silent Wave, depending on brand) motors, common in DSLR lenses, are virtually silent and usually fast—huge benefits particularly for wildlife photographers but also those who shoot weddings, sports, action and live performances. Linear stepper motors common in mirrorless (and some DSLR) lenses can provide fast, smooth and silent autofocus while shooting video.
Lens Care Essentials
Caring for your lenses is the key to maintaining their image quality and prolonging their lifespan.
To prevent damage to the glass, keep lens caps on your lenses when they’re not in use. Clear, screw-on filters and an additional layer of protection even while you’re shooting.
It’s a good idea to also keep each lens in a soft pouch or padded compartment in your camera bag so they don’t scratch against other hard objects.
Invest in a cleaning kit to keep your lenses shooting sharply and functioning smoothly. An air blower will safely remove dust and dirt; after that, clean the glass using lens solution applied with a clean microfibre cloth. A lens pen is handy for absorbing any remaining smudges. (For more info on lens cleaning products and techniques, visit our Cleaning Essentials page.)
Find Out More
We know it’s not always easy to shop for camera lenses online. They’re a serious investment with lots of factors to consider, and every photographer has unique preferences and priorities. We hope this guide helps to answer some of your questions; however, if you have more, feel free to contact or visit us.