When looking to buy a new lens, or at a lens you already own, you may have wondered what the numbers on a camera lens mean. Manufacturers stamp lenses with details about the glass. It can show the aperture, focal length, and other specifics about the lens.
In this article, we will cover what the numbers on your camera lens mean. It may seem complicated, but you can learn to decode the manufacturers’ shorthand with a few hints.
Let’s have a look at the most common letters and numbers on camera lenses.
F Numbers Mean Aperture
F stands for F-stop or the speed of your lens. This is the widest aperture of the lens. Your lens may or may not have the “F” printed on it. You may see a number, a slash, and another number (# / #). The first number is the F-stop. Some manufacturers express the F-stop as a ratio, 1: ##. A lens reading 1.8 / 55 (or 1:1.8) means that the maximum aperture of the lens is F/1.8. Lenses with wider apertures let in more light and are generally more expensive.
On telephoto lenses, there may be a range of numbers either side of the slash (## – ## / ## – ## or 1: ## – ##). A lens reading F/4.0-5.6 means that as the lens zooms, the aperture narrows. The maximum aperture is F/4.0. But when fully zoomed in, the aperture narrows to F/5.6. The zoom lenses that do not change the aperture as they zoom are more expensive.
There may be other letters with the “F” on some lenses. These letters are often used to separate similar lenses having different features within the same system. For instance, “FE” for Sony identifies the lens as a full-frame, E-mount. “FD” is an older version of Canon lenses replaced by an electronic “EF” mount.
mm Numbers Mean Focal Length
The focal length of your lens is in millimetres (mm) on the lens. Your camera lens may or may not have the “mm” printed on it. You will see a number, a slash, and another number (# / #). The second number is the focal length. A lens stamped 1.8 / 55 means that the focal length is a fixed 55mm.
Prime lenses have only one focal length, while zoom lenses have a range of focal lengths. Smaller numbers are wide-angle lenses. The larger the number, the more zoomed in you can get. A reading of 18-55mm is a focal length range. It means that you can change your focal length. The widest angle is 18mm, and you can zoom in to 55mm. Common zoom lenses are 16-35mm, 24-70mm, and 70-200mm. But zoom ranges vary by manufacturer.
Ø Numbers Mean Diameter
The symbol that looks like a circle with a line through it (Ø) means diameter. This is the measurement, in millimetres, around the outside circle of your lens. Ø72 means that your lens is 72 millimetres in diameter. You need to know the size of your camera lens if you are buying a filter or a lens cap.
Meters and Feet Numbers Mean Focusing Distance
Your lens may have a number that is in meters and feet (#m / #ft). This is the minimum focusing distance for the lens. This number matters mainly for photographers who like to get close to their subjects. A camera lens that shows 0.9m / 2.96ft will focus at 0.9 meters or 2.96 feet. The numbers are equal but expressed in two different measurement systems. If you move the lens closer than 0.9 meters to the subject, the camera cannot find focus. On a zoom lens, the focusing distance may be a range of numbers. A lens reading 0.5m / 1.64ft-0.8m / 2.63ft means that as the lens zooms, the focusing distance lengthens. At the widest focal length, the focusing distance is 0.5 meters. But when zoomed in, the focusing distance is 0.8 meters.
Macro lenses can take photos of small things or photograph very fine details. A 1:1 magnification means that the real-life image is the same size as it is on the sensor. If the ratio is 2:1, then the lens makes the subject twice the size of the sensor. If the ratio is 1:2, the subject is half the size of the sensor. You may have the option to change the ratio on your lens.
Other Lens Features
Camera manufacturers often stamp other letters onto their lenses. These show special features of the lens. On Sony, “G” stands for “Gold” or the highest-quality version of the lens. “OSS,” which identifies the lens having optical stabilisation. “USM” on Canon lenses stands for “Ultrasonic Motor”, which assists the focusing system. “AF-S” in the Nikon system also means that there is a motor inside the lens. “ED” refers to the type of glass used on Nikon lenses.
The manufacturer will also tell you if this is a second version of the lens. Usually, this is expressed with the Roman numeral II. These lenses are usually an improved version of an older lens.
There are all sorts of letters that lens manufacturers use. In general, lenses with special features will cost more. Be very careful to look at all letters when buying a lens. Some letters identify different mounts within the same system. Canon uses “RF” to refer to their new mirrorless lenses. These do not mount on Canon cameras with mirrors.
These letter combinations are unique to the manufacturer. Here are a few ways different lens makers abbreviate lens specifications.
Camera Lens Buttons and Dials
Many lenses have buttons and dials that include numbers and letter abbreviations. On a zoom lens, you will have a ring that changes the focal length. Sometimes you will also have an aperture dial on the lens. Twist the dial to change the aperture. Some lenses let you turn on and off image stabilisation. Landscape photographers often turn this off when mounting a camera on a tripod. You may alter the focusing distance or toggle between auto and manual focus on the lens. It is important to know what all the letters and number of your camera lens mean.
Each lens manufacturer has a unique way of labelling lens features. At the least, you can expect to see the maximum aperture (f-stop) and focal length labelled on the lens. You may also see other features of the lens, including the mount.
When buying a new lens, look carefully at every letter and number. Each holds valuable information. One letter (or lack of letter) may change the lenses’ value by hundreds of dollars.