How To Read a Camera Lens? 

How To Read a Camera Lens featured photo

If you want to buy a new camera lens, you are likely to encounter different letters, numbers, and abbreviations. It can be overwhelming to determine what these figures mean. However, it is important to read a camera lens to understand its features and specs better.

To read a camera lens, you must learn the definitions of the numbers and letters on a camera lens. The numbers describe the focal length, aperture, and diameter of a lens, among other features. Meanwhile, the letters stand for the mount type, autofocus motor, and stabilization system.

Camera lens manufacturers also use distinct marketing abbreviations for their products, which makes things more confusing. This article will teach you the meaning behind these terms, so you can learn how to read a camera lens. 

What Do Numbers on a Camera Lens Mean?

When shopping for a new camera lens, you will notice different numbers stated on the spec sheet. You will also find these figures on the lens barrel itself. But what do they really mean? Below, we will guide you through their definition.

Focal Length

Focal Length of a Camera Lens

The focal length of a lens is expressed in one or two numbers followed by the letters “mm” or millimeter. However, the millimeter marking could be missing in some lenses. Instead, a number, a slash, and another number (# / #) may describe the focal range of a lens.

If you can only see a single number, you can safely assume it is a prime lens. That means it has a fixed focal length, which lacks zoom functionality.

But if you notice two numbers on the lens barrel, you have a zoom lens. The two values represent the multiple focal ranges you get with the zoom. The smaller number represents the shorter focal length, while the higher value is the longer focal length. For example, in an 18-55mm zoom lens, the first figure is the wide focal length, while the second one is the telephoto end of the lens.


The next number you will notice beside the focal length is probably the aperture. It is the lens opening that determines how much light enters the image sensor. It is expressed in f-stops or f-numbers. The lower the number, the larger or wider the lens opening.

All camera lenses include the widest aperture you can get.

This factor is usually expressed in a number, a slash, and another number (# / #). The first figure is the actual f-stop as a ratio, while the second one is the focal length. For example, the numbers f/2.8 / 50mm mean that the lens has a maximum aperture of f/2.8 and a 50mm focal length.

However, some manufacturers use two numbers to describe the widest aperture of a camera lens. These are common in telephoto lenses, which have a variable maximum aperture. For instance, a reading of f/4.0-5.6 means that the aperture gets smaller as the lens zoom. So if you have a 70-200mm lens, you will get a maximum aperture of f/4 at 70mm. But if you zoom in at 200mm focal length, you can only use f/5.6.

Lens Diameter

The diameter of the lens is the measurement of the outside circle of the lens. Similar to the focal length, it is measured in millimeters. But instead of the “mm” designation, the Ø symbol describes the lens diameter. It is usually located in front of the camera lens or on the side near the top.

Also known as the filter diameter, the lens diameter also determines the size of the accessory you must use. For example, if you have a lens with Ø72, buy a filter or lens cap of the same size. Doing so ensures compatibility.

Focus Distances

Some lenses have numbers in meters and feet (#m / #ft). They are the minimum focusing distance for the lens. Both numbers are important for macro photographers who like to get near the subject. If you move the lens beyond these values, the camera and lens are unable to focus on the subject. 

For example, a prime lens with a 0.9m / 2.96ft designation can focus at 0.9 meters or 2.96 feet from the subject. These numbers on a camera lens have equal value. However, they are expressed in different measurement systems. 

A zoom lens may have a range of numbers to describe the minimum focusing distances, such as 0.5m / 1.64ft – 0.9m / 2.96ft. That means the closest focusing distance is 0.5 meters at the widest focal length. However, it can change to 0.9 meters if you use the telephoto end of the lens.

Magnification Ratio

Certain types of lenses include the magnification ratio in their specs list. These are usually macro lenses that capture images of small subjects or fine details.

Macro lenses have a magnification ratio of 1:1, 2:1, or more. Besides ratio, they can also use decimals to describe the magnification value. For instance, a 1:1 ratio is equivalent to 1x magnification. That means the sensor projects an image that is the same size as the subject in real life.

What Do Letters on a Camera Lens Mean?

Camera lenses also have several letter markings. These can stand for several features and specs. Below, we will also teach you the meaning behind these letters.

Mount Type

The mount type determines the compatibility of your lens with a camera. It comes in different letters, each unique to the manufacturer.

We included some common mounts across various lens manufacturers below.

  • Canon – EF for full-frame cameras, EF-S for crop sensor cameras, RF for mirrorless cameras
  • Nikon – FX for full-frame cameras, DX for crop sensor cameras
  • Sony – FE for full-frame cameras, E for crop sensor cameras
  • Sigma – DG for full-frame cameras, DC for crop sensor cameras
  • Pentax – FA for full-frame cameras, DA for crop sensor cameras
  • Tokina – FX for full-frame cameras, DX for crop sensor cameras

You can usually find these letters on the front of the camera lens. Make sure to research the mount types compatible with your camera before buying a lens.

Automatic or Manual Focus

Automatic or Manual Focus

Most camera lenses include a switch on their side that comes with an “AF/MF” label. So what does AF/MF mean on the camera lens? These letters stand for autofocus and manual focus.

As its name suggests, autofocus automatically follows and keeps the subject in focus within the frame. On the other hand, manual focus gives you complete control over the focus area or depth of field.

The AF/MF switch enables you to enable or disable the autofocus and manual focus features. It comes in handy if you want to control the final look of the image.

Autofocus Motor

The autofocus mechanism of a lens uses internal motors to work. These components have different names or abbreviations depending on the lens manufacturer. 

Below are just a few letters that various camera manufacturers use. 

  • Canon – STM for stepper motor, USM for ultrasonic motor
  • Nikon – SWM or AF-S means silent wave motor, AF-P is pulse or stepper motor
  • Sony – SSM for SuperSonic motor, SAM for smooth autofocus motor
  • Sigma – HSM or Hyper Sonic motor
  • Tamron – PZD or PieZo Drive autofocus motor

Image Stabilization

Some camera lenses have a built-in image stabilization system. It reduces camera shake when shooting handheld or using slow shutter speeds. It ultimately gives you steady and sharp images.

The letters on the camera lens tell you whether it has stabilization capabilities or not. These abbreviations also vary depending on the brand or manufacturer. 

  • Canon – IS for Image Stabilization
  • Nikon – VR for Vibration Reduction
  • Sony – OSS for Optical SteadyShot
  • Sigma – OS for Optical Stabilization
  • Tamron – VC for Vibration Compensation
  • Tokina – VCM for Vibration Correction Module

What Are the Other Abbreviations and Letters You Must Know?

Camera brands include other letters and numbers in their lenses. These represent the special features of the lenses.

Below are the ways different brands use abbreviations for lens specs.

Professional Lenses

Professional Lenses

Different camera brands give their professional lenses unique names, which are abbreviated in letters. These professional-grade lenses have higher-quality glass, more durable construction, and faster autofocus motors than consumer-grade lenses. They are usually designed for full-frame cameras. Hence, they suit professional photography.

Here are some lens brands and the abbreviations they use for different lens series.

  • Canon – L for luxury lenses
  • Nikon – Instead of letters, a gold ring around the barrel indicates pro-grade Nikon lenses
  • Sony – G for gold lenses, ZA for Zeiss Alpha branded lenses
  • Sigma – EX for professional prime lenses, A for Art lenses, C for Contemporary lenses
  • Tamron – SP for super performance lenses 
  • Tokina – ATX-Pro for professional lenses

Low-Dispersion Lenses

Several photography lenses have low-dispersion glass elements. They minimize the effect of chromatic aberration or color fringing. It is a type of distortion that leaves unwanted color near the edges of objects in an image.

Manufacturers use different letters or abbreviations for a low-dispersion lens.

  • Canon, Nikon, Sony – ED for extra low-dispersion glass
  • Sigma – APO for an apochromatic lens, SLD for special low-dispersion glass, FLD for fluorite low-dispersion glass
  • Tamron – LD for low-dispersion glass, XLD for super low-dispersion glass
  • Tokina – SD for super low-dispersion glass

Lens Version

You will notice that some lenses have a Roman numeral, such as I, II, or III. This letter or number describes the version of a lens.

“I” is the original lens, while “II” and other higher Roman values describe the upgraded version. The latter has the same features as its predecessor. However, it tends to have higher-quality optical glass and a more durable build. The only downside is its higher price tag. 

You usually cannot buy the older version of the lens in stores. However, you can still purchase it in second-hand camera stores.

Learn how to use 18-55mm lenses.


Expect to see different letters and numbers when shopping for a new camera lens. Each manufacturer uses these figures to tell the features of their lenses.

Learning how to read a camera lens is essential before finalizing your purchasing decision. You can start with the basic letters as they are usually shorter names for different specs. Then, you can memorize the various numbers that stand for basic lens features. 

Do you have other questions about the letters and numbers on a camera lens? Feel free to send your queries to our contact page today!