If you are new to photography, you might find yourself wondering what all of the different numbers, letters and symbols on your lens mean. They may seem complicated on first glance, but they're really easy to understand once explained.
In this post, I will show you a few examples of standard lenses, and explain to you some of the most important numbers and letters you have on your lens.
The standard unit of measurement for the focal length of a lens is millimeters, so when you see "mm" following a number on a lens, you will know that the number is the focal length of the lens. Here is a 24-70mm lens:
And an 85mm:
When you see a 1: followed by a number, this represents the aperture of the lens. In this case, the numbers read 1:2.8 which means that this 24-70mm has a wide open aperture of f/2.8:
In some cases with zoom lenses, you will see two numbers following the 1:, as in the example below, which shows an aperture of 1:3.5-4.5. What this means is that, when zoomed in, the widest possible aperture changes from f/3.5 to f/4.5, So, for this lens, when zoomed out at 10mm, the widest aperture is f/3.5, but zoomed in to 22mm, the widest possible aperture is f/4.5:
AF / MF
On the side of your DSLR lens, you will see the letters AF/MF (Canon) or M+A/M (Nikon) with a small white line and switch beneath. This allows you to change your lens from Autofocus to Manual focus:
Not all lenses have the same diameter, and knowing the diameter of your lens is important when purchasing filters and lens hoods.
Here is an example of what the diameter sign looks like on your lens:
As you can see, this Sigma 35mm lens has a 67mm diameter, therefore you would need a 67mm filter, as well as a lens hood to fit a 67mm diameter lens.
You will sometimes see II at the end of the lens name/description, this means that it is the second generation of that particular lens.
USM / HSM
These letters tell you what type of Autofocus motor is in your lens. USM = Ultrasonic Motor and HSM = Hypersonic Motor. They are the same thing, but each manufacturer uses different terminology.
IS / VR
Image Stabilizations (IS - Canon) and Vibration Reduction (VR - Nikon) denote lens technology designed to reduce the effect of camera shake. Not all lenses come equipped with this technology, but you will know if your lens is, because it will have the abbreviations "IS" or "VR" near the glass on the lens, or you will see "Image Stabilization" or "Vibration Reduction" on the body of the lens.
Entire blog posts have been dedicated to the various abbreviations on lenses because there are so many abbreviations used among lens manufacturers. The letters on the lens are simply used to describe specific features, such as the type of technology the lens uses, the type of camera to which the lens can be mounted, or the grade of the lens.
Canon uses abbreviations such as EF and EF-S, while Nikon uses AF and AF-S to describe their lenses.
If you are unsure of what these abbreviations mean, a quick Google search should tell you exactly what you have.