Each part of the lens serves an important purpose:
Not every lens has all seven of these features, and other lenses have many more than this. However, the lens above is fairly representative of modern zoom lenses.
Most lenses today are named in a relatively standard way: brand name, lens type, focal length (in mm), maximum aperture, other lens features/abbreviations.
For example, the official name for one of Nikon’s professional zooms is the “Nikon AF-S 24-70mm f/2.8 E ED VR” lens. Canon’s equivalent is the “Canon EF 24-70mm f/2.8 L II USM” lens.
The most important terms are focal length and maximum aperture. In other words, the “mm” and the “f/number” terms. These numbers are the most directly related to the types of photos you will be able to capture with the lens. (I’ve got a full section later on each one and why it is so important.)
What about the abbreviations at the end of the lens name? They still matter, denoting the extra features offered by each lens. For example, the “VR” term in the Nikon lens stands for “vibration reduction,” which stabilizes the lens for handheld shooting. However, these other terms are usually secondary in importance. Some don’t even refer to a specific feature, but instead are solely for advertising value (such as “L” on the Canon lens, which simply means it is one of Canon’s high-end lenses).
The main exception to the “mm and f-number matter most” rule is when you’re dealing with specialty lenses. With fisheyes, macro lenses, tilt-shifts, and so on, your main reason for buying the lens has more to do with its unique feature than anything else.
So, what do all the abbreviations at the end of a lens name stand for? Each company labels its lenses in a different way, with potentially dozens of abbreviations per manufacturer – too many to fit in this article. However, we’ve covered all the various terms for many lens manufacturers the following guides:
The most important specification for most lenses is their focal length – in generic terms, how far “zoomed in” the lens is. Focal length is written in millimeters.
Some lenses only have a single focal length. These are known as prime lenses. A popular example is the 50mm lens – a very common first prime lens for photographers, thanks to its high usefulness and low price.
Other lenses are zoom lenses, meaning that they cover a range of focal lengths. For example, the most common zoom lens on the market is an 18-55mm kit lens (sometimes 18-50mm or similar). These lenses zoom from a relatively wide angle (18mm) to a moderate telephoto (55mm). If you divide the lens’s longer focal length by its wider focal length (like 55/18), then you get the lens’s zoom ratio (like 3x).
A few specialty lenses on the market fit somewhere between primes and zooms, such as the Leica 16-18-21mm f/4 lens. This lens covers three specific focal lengths – 16mm, 18mm, and 21mm – but none of the focal lengths in between. This is contrary to a normal zoom lens, which smoothly zooms from its widest to longest focal length.
The technical definition of focal length is a bit messy, and beyond the scope of this article. Elizabeth wrote a comprehensive guide to focal length that explains everything at a technical level.
I’ll note quickly that the sensor size of your camera contributes to the apparent focal length you’re using. This is because small camera sensors are like crops from a large camera sensor. Put the same lens on both, and the lens will appear more zoomed in on the small sensor.
Cameras with a larger crop factor (i.e. smaller sensor) will exhibit this effect the most. You can calculate the exact amount simply by multiplying your lens focal length by your crop factor. So, an 18-55mm lens used on a Nikon DX sensor – which has a 1.55x crop factor – is equivalent to a 28-85mm lens on a larger full frame camera sensor.
This is also why you can’t just say that a 28mm lens, for example, is a wide-angle. On some cameras, it is more like a medium lens, and on others it’s even a moderate telephoto. You have to specify 28mm equivalent.
Here’s a general guide:
The other critical term in a lens name is the “f/number” term, which stands for the lens’s maximum aperture.
First, if you are unfamiliar with the concept of aperture, I recommend reading our beginner’s guide to aperture. In short, aperture describes the “pupil” of your lens. Just like the pupil in our eyes, the aperture in a lens will let in more or less light. It is quite an important specification.
Many photographers don’t realize that aperture is written as a fraction. This is why f/2 is larger than f/4 – it’s just like 1/2 being larger than 1/4. Expensive lenses often have large apertures to let in a lot of light (again, like a large pupil). For that reason, a 24-70mm f/2.8 zoom is going to be more expensive than a 24-70mm f/4 zoom in practically every case.
In general, prime lenses have a larger maximum aperture than zooms, especially at a given price. It’s one major reason why photographers use primes. Zooms usually max out at f/2.8, while plenty of primes on the market go to f/1.4 and sometimes wider. This means prime lenses can let in 4x as much light as the best zooms.
Of course, even though a lens name will include its maximum aperture, you aren’t restricted to using that aperture alone. You can always change the aperture to be smaller if you want. Almost all lenses go down to at least f/16, while many allow f/22, f/32, and beyond. This is called minimum aperture.
Minimum aperture isn’t nearly as important as maximum aperture, though. It’s why you only see maximum aperture in the lens name. If you use extremely small apertures, especially f/22 and beyond, you start to add blur throughout your photos and darken them more than you’d normally want.
As with focal length, here’s a general guide to aperture:
The other reason why maximum aperture is so important is that it impacts your depth of field. Large apertures like f/1.4 and f/2.8 will give you more of a “shallow focus” effect, where the background is blurred and your subject is sharp. This is very common to see in portraiture and still life photography.
Depth of field is also influenced by the lens’s focal length. Telephoto lenses have a shallower depth of field than wide angles. So, if you really want to blur the background of your photo as much as possible, you’ll want at least a 50mm f/1.8, and probably something like an 85mm f/1.8, 85mm f/1.4 or 105mm f/1.4. But those lenses also get progressively more and more expensive.
Some zoom lenses have a different maximum aperture at their wide angle and telephoto ends. These are called “variable aperture” lenses. For example, the 18-55mm zoom I talked about earlier usually is f/3.5-5.6 variable aperture. If you shoot at 18mm, you can use an aperture as wide as f/3.5. If you shoot at 55mm, you can use an aperture as wide as f/5.6. (At focal lengths in between, your maximum aperture gradually changes from f/3.5 to f/5.6.)
Variable aperture lenses don’t have the best reputation. In part, this is because it is annoying to have different aperture limitations throughout the zoom range. But all lens designs have trade-offs, and variable aperture is hardly the worst compromise out there.
In fact, these lenses can be smaller and less expensive than constant aperture zooms, making them quite reasonable in many cases. So, don’t avoid variable aperture zooms by default. Instead, look to other features of the lens, too, to see if it’s a good fit for you.