What Do the Numbers On A Camera Lens Mean?

No matter what the brand, lenses have a lot of numbers and letters printed all over them. Although it seems a little cryptic at first, there’s a lot of valuable information your lens is trying to tell you. So what exactly do all the numbers on your camera lens mean?

The numbers on a camera lens will tell you all the information about the lens. From the focal length, max aperture, focus distances, lens type, thread diameter, and more. By understanding these numbers, you can better decide which lens to use for a particular photo.

Understanding The Numbers And Letters On Your Camera Lens

Now obviously, there’s a lot more to explain than what all the numbers display. To help you better grasp what the numbers on a camera lens mean, let’s talk about each area individually.

Focal Length

The focal length is that one thing everyone uses when describing lenses. “That’s my 16-35 lens” or “I’m using a 70-200”. These numbers tell you how wide the field of view will be on a particular lens. In fact, all the numbers are labeled right at the base of your lens, closest to the camera.

Each of these numbers represents a different focal length. On zoom lenses, you’ll see a few different focal lengths written on your lens. As you twist the lens barrel, the marker will indicate which focal length you’re using. On prime lenses, there is only one focal length since they have no zoom capabilities. In this case, the focal length is usually listed somewhere in the middle of the lens.

Focal lengths are one of the biggest aspects of photography. Just by zooming in or out, you will totally change the look of your photo. That’s why so many photographers are absolutely obsessed with lenses. After all, the lens you use plays a more creative role in your photo than the actual camera body!

Understanding Focal Lengths

Figuring out whether a focal length will give you a wide or zoomed perspective is pretty intuitive. The smaller the number (eg: 16mm), the wider field of view you’ll have. With a longer focal length (eg: 200mm), you can zoom in to further away objects.

There isn’t one ‘perfect’ focal length in photography, and you’ll often bounce around between different ones. As you begin to build your kit of lenses, it’s most important to have all your focal lengths covered from ultra-wide to zoomed in. That way, you always have the opportunity to capture any shot you want!

An easy way to understand focal lengths is to start at 50mm. On a 50mm lens, your camera will have approximately the same field of view as what you see with your eyes. Now thinking about what you see now, imagine a 25mm lens that would be twice as wide as what your eyes currently see. On the opposite side, 100mm would be twice as zoomed in compared to what your eyes see.

I talk about focal lengths extensively in Goodbye Automatic and how each of them will drastically change your image. Since you’re new to this, let’s make it easy and compare a few different images with a wide, mid-range, and zoomed focal length.

With a wide-angle of 14mm, my camera can see just about everything around me. The perspective is far wider than your eyesight, but it creates a cool effect.

14mm

At a mid-range focal length of 50mm, things start to look a bit more natural. It does appear a little bit zoomed in, but the perspective is relatively similar to your eyes.

50mm

At a zoomed-in focal length of 200mm, things that are physically far away from my camera appear extremely close. With a longer focal length, it’s almost like using binoculars for your camera.

200mm

Are Focal Lengths The Same Across All Cameras?

Putting camera brands to the side, you can only buy only two types of cameras: a full frame or crop sensor. There are other variations of a crop sensor such as a micro four thirds, but each essentially garners the same result. These two camera types refer to the size of the camera’s sensor, aka the thing that actually records light and captures a photo. Since a crop sensor has a physically smaller sensor than a full frame, focal lengths will appear more zoomed in on a crop sensor.

That is if you’re using the wrong type of lens.

As I’ll discuss later in this post, there are lenses designed for both crop sensor and full frame cameras. The caveat here is that full frame lenses are also compatible with crop sensor camera bodies. That’s where the problems come into play.

Since a crop sensor has around a 1.6x crop (this varies between camera brands), any focal length it sees with a full frame lens will appear 0.6x more zoomed in than on a full frame.

For example, a 16mm full frame lens would appear as a 25mm lens on a crop sensor. You can do this math for any focal length by going:

Focal Length X Crop Factor (1.6x) = Equivilent Focal Length

I explain crop factor and how it affects your focal length extensively in this video:

Considering the crop factor is an important part of understanding the focal length of your camera lens. Especially if you’re about to purchase a new lens, you want to make sure you’re getting the focal length you need!

Focus Distances

The next important number on your camera lens you need to understand is focus distances. These numbers are usually displayed on top of the lens barrel when it’s mounted to your camera. You’ll see an “M” for Meters and “FT” for feet with a series of numbers that change as you rotate the focus ring. These are your focus distances.

There are two lines of numbers that align with the corresponding measurement for meters or feet. In the center of it all is a dash that points to certain focus distances. This dash tells you how far away your focus is set.

When your camera is finding focus, it’s physically moving the glass elements in your lens to help incoming light converge. Depending on how far away your subject is, the reflected light from your subject will converge at different distances.

To think of it in a less complicated way, the focus distance should match up to the approximate distance between your camera and the subject.

When you’re shooting a wide-open scene, the lens will likely find focus at an infinity icon. With your focus set to infinity, this means it’s set for just about anything far away from your camera.

It won’t make a difference after a certain distance whether your camera is focused on something 200m away or 300m away. Anything further away will all look in focus when your camera lens is set to infinity.

On the opposite end of this is close focus distance. When you want to get close to something, your close focus will tell you exactly how far away you need to be to maintain a sharp photo. By rotating your focus ring all the way to the smallest distance, you’ll see how close your lens can focus to. On some lenses, this can be only a few inches, while others, it might be an entire meter or more!

Focus Switch

If your camera lens has autofocusing capabilities, you’ll see a switch somewhere on the barrel that reads “AF” for autofocus and “MF” for manual focus. By moving this switch to one side or the other, you can choose how your lens focuses.

With autofocus, your camera will automatically find focus for you based on your preset autofocus point. For general use in brighter conditions, autofocus is the easiest way to take photos.

When you need to be more specific with your focus or are shooting in low light, that’s where manual focus shines. As the name suggests, manual focus requires you to rotate the focus ring to get the proper focus manually. Since autofocus doesn’t always work great in low light situations, manual focus is usually the way to go.

No matter which focus mode you want to use, it’s easy to switch back and forth with the focus switch.

The Widest Aperture

Besides focal length, the aperture is another extremely important aspect of any camera lens. Without numbers on a camera lens, it would be extremely hard (if not impossible) to know exactly what the aperture range is.

On all camera lenses, you’ll see something along the lines of 1:2.8 or 1:4-5.6. These numbers aren’t telling you a ratio, but instead, what the widest aperture (or F-stop) for that lens is. Different brands will have this number displayed in different places, but it will still appear in the same ratio format. In this example, the lens shows 1:2.8 on the front of the lens to tell me it has a widest aperture of F/2.8.

Depending on your camera lens, these numbers might vary. If you see something like 1:4-5.6, this means your lens has a variable aperture. On some lenses, the widest aperture will change depending on the focal length. In the case of this lens, at the widest focal length, you could reach an aperture of F/4. However, at the most zoomed focal length, you would only reach a widest aperture of F/5.6. This isn’t the most ideal, but that’s the big difference between cheap and expensive lenses.

If you’re not familiar with aperture, I’d highly recommend reading this post on using aperture in photography to get up to speed!

Thread Diameter

A number on your camera lens that comes in extremely handy is the thread diameter. This number will tell you the circumference of your lens threads so you can purchase the right filter for your camera. Since every lens can have a different element diameter, it’s crucial you get the same size filter; otherwise, it won’t fit properly!

On most lenses, you will find the thread diameter displayed on the front element of the lens. It will have an O with a / through it and a measurement size in millimeters. For this lens it has a thread diameter of 82mm.

Even as a beginner photographer, taking advantage of lens filters is something I encourage everyone to try. To help get you started, I wrote a list of the best types of lens filters for beginners to use.

If you’re not into creative filters, I would suggest you look into getting a UV filter to protect your camera lens.

As you start to purchase your first filters, that’s where knowing the thread diameter of your lens comes in handy!

Mount Type

One of the most cryptic numbers and letters on a camera lens is around the lens mount type. Unless you’re familiar with your camera brand and what mount types they have, it just seems like a bunch of jibberish.

EF-S, DT, FX, what?

Here is a list of common full frame and crop sensor mounts across lens brands.

  • Canon: EF (Full Frame) EF-S (Crop Sensor)
  • Nikon: FX (Full Frame) DX (Crop Sensor)
  • Sony: FE (Full Frame) E (Crop Sensor)
  • Sigma: DG (Full Frame) DC (Crop Sensor)
  • Tokina: FX (Full Frame) DX (Crop Sensor)
  • Pentax: FA (Full Frame) DA (Crop Sensor)

You will usually see these letters printed on a camera lens near the front element. When you’re looking to buy a new lens online, look at these mounting types beforehand, so you know it will work for your camera!

Stabilization

Some lenses have built-in stabilization capabilities that make a huge difference when shooting handheld. With internal stabilization, you can use a slower shutter speed while shooting handheld and still get a crisp image. Especially when you’re shooting events and don’t have time to set up a tripod, a stabilized lens makes a big difference.

But what numbers on your camera lens will tell you whether the lens has stabilization capabilities or not? Well, there are a few letters that will tell you exactly that. Here’s a helpful list of stabilization acronyms across different lens brands:

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

If you’re not familiar with shutter speed and when it is too slow to shoot handheld, be sure to check out this ultimate guide to shutter speed in photography!

Lens Focal Length Lock

On some zoom lenses, you might have a lock switch on the lens barrel. This switch is used to lock the lens in place at its widest focal length to be stored more safely. When you put the camera lens away in your camera bag, it can extend the barrel as it gets bumped around. To prevent this from happening, you can use the lock switch to keep the lens in it’s lowest profile. That way, you can guarantee some added security to your lens while on the go!

Now You Understand The Numbers And Letters On A Camera Lens!

What likely seemed a confusing pile of jargon all over your camera lens now seems a lot more clear than it did before. By learning what the numbers on a camera lens mean, you can better decide which lens and use or purchase in the future! Even with all the acronyms, it works around the primary functions of a camera lens. If you feel too overwhelmed by some of this, try to only focus on the focal length, aperture, and mount type. After all, those are the three most important parts of your lens!

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– Brendan 🙂