What Does mm Mean on Camera Lens?

In the world of camera lenses, “mm” means millimeters and represents the lens’s focal length. Some lenses have a fixed focal range, while others have a range of millimeters, representing an adjustable range.

I’m Caleb, and I have around five years of photography experience. As I’m mainly a sports photographer, I’m very familiar with the requirements for a great lens.

In this article, I’ll explain what the mm numbers on camera lenses mean and how this plays into choosing the right lens. If you’re new to buying lenses and want to ensure you get the right one, keep reading for a simple explanation.

What Does mm Mean on Camera Lens?

The “mm” number found on camera lenses stands for millimeters. Basically, the number is there to tell you the focal length of the lens. This significantly impacts the lens’s performance by determining which ranges the lens works best at.

Simply put, the focal length is a measurement that tells you how much “zoom” the lens has. Lenses with a smaller mm number, like 24mm, offer a wider view and can fit more into the frame. Lenses with a larger number, such as 200mm, make objects appear closer.

There’s no objectively superior focal length. Different lenses excel at different types of shots. For example, a wide lens might be very good at capturing sprawling landscapes, while a more zoomed lens is often better at shooting individual subjects.

Why Does Focal Length Matter?

Focal length matters because it greatly impacts what your final pictures look like. It decides many of a lens’s inherent strengths and weaknesses and tells you what types of photography a lens might be suited for.

Generally, you’ll need a shorter focal length for wide-angle shots and a longer length for narrower, more focused ones. Longer focal lengths are also useful for getting close-ups of distant subjects, vital in some niches like sports photography.

By considering focal length, you can quickly tell if a lens fits your needs and creative style.

Prime Lenses vs. Zoom Lenses

You might have noticed that some lenses have only a single mm number, while others have a pair of numbers indicating a range. For example, a lens might have a focal range of 24-70mm or 70-200mm.

Lenses with a fixed focal length are also called prime lenses. Their focal length is always the same and is non-adjustable. On the other hand, Zoom lenses can change their focal distance to any number within the listed range.

Zoom lenses are popular for their convenience. Because of their versatility, it’s possible to carry one zoom lens that serves the same role as two or three different prime lenses. They aren’t without drawbacks, however.

Prime lenses are sometimes cheaper and often have better image quality and maximum aperture. Ultimately, there’s no right or wrong choice between prime and zoom lenses. It depends on your goals and how much you value convenience.


Here are some frequently asked questions that have come up around the subjects of focal lengths and lenses.

What Is A Good mm For A Camera?

That depends on what you’re trying to do. There’s no such thing as a universally ideal focal length because the various focal lengths excel at different types of shots.

What Is The Best Focal Length For A Beginner?

If you’re just starting out, you might want to start with a 24-70mm zoom lens or a 50mm prime lens. These options are fairly neutral, allowing you to try out various shot types without the focal length getting in the way.

Is Lower mm Lens Better?

Not necessarily. A lower mm number indicates a wide lens, which can be helpful in some situations but isn’t better inherently. Lenses like these are most useful when you want to fit a lot into the frame.

Final Thoughts

Understanding focal lengths is key to understanding lenses as a whole, but it doesn’t have to be complicated. Remember, a lower mm lens will produce wider shots, while a higher mm lens makes for narrower, more zoomed-in ones.

Do you have a preferred focal length to use in your own photography? Let us know in the comments!

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