What Do The Numbers On Lenses Mean?

If you thought DSLR cameras had confusing terms, you haven’t seen anything at all. With so many different brands (including third party lens) there’s an alphabet soup of letters and numbers on camera lenses. So what do the numbers on lenses mean after all? As we said, there are all sorts of brands and they all name their features a little bit different.

Beginners may find it a bit confusing with all these numbers, but it should only take you a couple of minutes to understand what every lens was designed for.

Most Important Lens Features

First, let’s go through the most important parts that all lenses share. I will also use actual products so you can imagine this much quicker.

1. Nikon 55-200mm f/4-5.6G ED IF AF-S DX VR

Brand Name: Pretty self-explanatory, the brand’s name is always first (Nikon)

Focal Length: The shortest and longest focal length (if it’s a zoom) the lens offers. In our case, 55mm is the widest and 200mm is the longest (55-200mm).

Aperture Size: Bigger apertures let in more light, and it’s usually reserved for more expensive lenses. In the Nikon example, the widest aperture is f/4 (available at 55mm), but when you zoom all the way to 200mm, the widest is now f/5.6. (f/4-5.6)

Since this isn’t a lens buying guide, I will only stick to actual markings on the lenses and won’t go into details about focal length, benefits and so on.

If you are interested in how to select the right lens for your camera we have a how-to guide that covers that in more detail.

2. Canon EF 50mm f/1.4 USM

This is a prime lens, meaning there is no zoom at all.

Focal Length: The Canon 50mm is always at 50mm, no matter how hard you try. It may sound like a bad deal if you think it’s all about zoom lenses, but primes usually contain higher quality elements and therefore give better image quality.

Aperture Size: One amazing advantage of prime lenses is the ability to use large aperture values! f/1.4 is perfect for low light and blurring the background, and it’s next to impossible to make a zoom lens with the same size, with the same aperture.

Now that we got that covered, it’s time to go through the most common lens acronyms/terms for each brand.

Canon Lens Terms

To understand the lens numbers for Canon they use around 7 unusual terms that you will come across when looking for lenses. They are either related to the mount, focusing or elements used.

EF – Standard Canon lens mount, fits on all of their DSLR cameras

EF-S – Only fits on APS-C type models (Rebel T3/1100D to EOS 7D)

RF – Refers to the lens mount type for many of their Mirrorless Camera models

IS – Image Stabilization, helps you at getting clear shots when using slow shutter speeds

USM – Ultra Sonic Motor, makes auto focusing quiet and more precise. Never a bad thing to have, but not a requirement for good focusing!

STM – New focus motor, also designed to be silent which is useful for video recording

DO – Diffractive Optics, allows Canon to make long lenses shorter and lighter

L – This is how Canon calls their most professional lenses (build and image quality are top notch).

Nikon Lens Terms

For those of you who shoot Nikon, things get a little bit more complicated. Most of their entry level models do not have an auto focusing motor built-in, so keep that in mind when shopping for a new lens.

FX – Fits and works perfectly with all Nikon’s DSLR cameras

DX – Designed for DX/APS-C models (D3100 to D7100)

Z – The type of lens mount for their Mirrorless Camera line

 VR – Vibration Reduction, does the same thing as Canon’s IS

SWM – (Silent Wave Motor) Just like Canon’s USM

AF-S – If a lens has an AF-S motor, it will focus properly with all DSLRs. If there isn’t any, then you will have to focus manually on the majority of DX models.

G – The lens has no aperture ring

ED – An extra dispersion element to improve image quality

IF – Internal Focusing, the lens doesn’t move while focusing (great for using polarizing filters)

N – Nano Crystal Coating, another feature to reduce optical issues