Written By:
Jeff

What Does The MM Mean On A Camera Lens: Explained

Published On:
July 26, 2021
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Like I always say, don't fret.  You don't know what mm means on a camera lens.  Not a big deal... I've got you covered with that.  That's the straightforward part.

Now, why do you need to understand what it means. More importantly, why do you need to know it, and what can you do with that information going forward? 

That's going to be what we're going to be talking about today.  We'll end the confusion about the mm markings on your lens then we will dive a little deeper and discuss why it's there and what you can do with that information.

You'll leave this article with more useful information than you asked for, when you showed up!  Let's get started, shall we?

MM Is Directly Related To Focal Length

What Does MM Mean On Camera Lens

Whoever invented camera lenses, was a genius. Now, whoever standardized the 'name' of a lens made it kinda difficult for the beginner to understand.

No worries, we've got you on this one.

You see, mm is the way we standardize a lens. The mm of a lens is its focal length. Whether it be a zoom lens or a prime lens, the mm of that lens is its focal length.

So, What If I Wanted A Wider Shot - What Camera Lens Would I Use?

What Does MM Mean On Camera Lens

Well, the focal length for a wider shot is pretty simple really.

  • The lower the mm, the wider the shot will be.
  • The opposite can be said for higher numbers.
  • The higher the mm, the tighter/narrower/zoomed-in look you will have.

**Going forward, I will be saying 'focal length' in place of anything that refers to the mm of a lens. This will allow the article to flow better/sound natural/make more sense.**

So, What Does MM Mean On A Zoom Lens

What Does MM Mean On Camera Lens

Zoom lenses aren't much different than a prime. It works much like a prime but with different focal lengths in the same lens.

Obviously, the major difference is a lens barrel and additional elements and glass (to allow it to zoom).

Once you've absorbed information here - head on over to our related article, How To Choose A Good Camera Lens, where we discuss not only about choosing, but the differences between zoom and prime lenses.

You can harness the look and reach of multiple focal lengths from a single lens (saves a ton of time, money, and resources by having a good zoom lens instead of only primes).

An example would be a Canon 24-70mm F/2.8 L. This is a lens with a focal length range between 24mm and 70mm.

How Does All Of This Work Inside Of The Camera?

What Does MM Mean On Camera Lens

While it's very complicated and mind-boggling how we've developed lenses capable of taking such amazing images... how it does it isn't too hard to understand.

Basically, the only job of a lens is to allow light to hit your camera sensor. Nothing more.

How the lens bends and manipulates the light that passes through it, determines overall quality .

The 'quality' at which a lens does this has a lot to do with price, as well.

Going back to MM...  It's actually a measurement.  MM is the distance from the point of convergence to your image sensor.  The point of convergence is the point within your lens all are waves of light converge - give you your beautiful colorful images.

For example - you have a 100mm macro lens.  The light that enters your lens converges 100mm away from your camera's actual image sensor.

It's this distance alone that creates different 'looks' or 'focal lengths'

Prime Lenses And Zoom Lenses - How Are They Different?

What Does MM Mean On Camera Lens

This is a loaded question - but I'm going to keep it in context with this article. We have a full-fledged article in the works that will explain, in detail, how zoom lenses and prime lenses are different.

But, zoom lenses are lenses that obviously zoom in and out. What it's doing internally is moving a glass element forward or backward (depending on the way you rotated it).

Remember how we talked about the point of convergence? Well, that's what a zoom lens is doing, moving that point of convergence back and forth - all within the lens itself.

Prime Lenses On The Other Hand...

What Does MM Mean On Camera Lens

...Are fixed focal length lenses. A fixed focal length lens doesn't have a barrel/glass element inside to move back and forth. It is literally fixed and doesn't move.

These are the 35mm, 50mm, or 85mm lenses you see on the market that're just that, 50mm. They don't zoom. The point of convergence remains the same and can't be changed.

Again, we will explain the advantages and disadvantages to either camera lens in the near future.

What About Wide Angle Lenses...

Well, simply put - it can do a lot of things.

Wide angle lenses are typically lenses that fall below 24mm. A wide angle lens will allow you to see much more of your surroundings than telephoto lenses would (lens with a long focal length).

A wide angle lens is commonly used for landscapes, Real Estate Photography, large outdoor events (markets, weddings), etc...

Telephoto lenses, on the other hand, are great when you need the reach (sports) - or when you want background compression (nice portraits).

Focal Length Recommendations

I thought it would be fitting for this article to have at least a little bit of a discussion into which focal length is the best depending on what type of photo you're taking.

Because a certain look will always come down to your lens focal length.

Also, remember, these focal lengths we're going to discuss are for a full frame camera. Your focal length will be different if you're shooting on a smaller sensor (like a crop sensor).

24mm Is A Great Semi-Wide Focal Length

What Does MM Mean On Camera Lens

This sits right on the edge of a 'normal lens' and a wide angle lens.

This is a great environmental focal length and should be used as such.

You should refrain from taking up-close photos of people's faces because of distortion.

Great all-around environmental/travel focal length.

50mm Is Considered The Most Versatile Of All Focal Lengths

What Does MM Mean On Camera Lens
What Does MM Mean On Camera Lens

50mm may be one of the most common, widely used focal lengths on the planet.

You wanna know why? Because it works so well at so many things.

We're talking portraits, street photography, automotive, even landscapes.

Not only that - the 50mm prime lens (all major manufacturers sell their own) is very affordable (less than $130 for a Canon) and produces amazing images.

You would never go wrong with owning a 50mm. Ever.

85mm Is The Go-To For Portraits (Even Though It's Not My Favorite)

What Does MM Mean On Camera Lens
What Does MM Mean On Camera Lens

The 85mm focal length is great for a lot of things because of the amount of compression.

As your focal length increases, compression starts to eliminate distortion. 85mm is the focal length that eliminates nearly all lens distortion on the human face.

Plus it's the focal length that allows you to move around a little bit and get the environment along with them if you wanted.

135mm The King Of Portrait Focal Lengths (In My Opinion)

What Does MM Mean
What Does MM Mean
What Does MM Mean

I started shooting portraits years ago with an 85mm like everyone else.

It wasn't until about a year and a half ago that I purchased a 135mm f/1.8 and have never looked back.

This focal length, of course, eliminates all distortion on a subject.

The best part - the compression and softness of the background/bokeh.

You can get a 'similar' look from a zoom, but the maximum aperture doesn't go nearly as low (f/2.8) So you're losing out on that and it can be almost twice as expensive.

Canon and Nikon sell a 200mm prime lens (f/2) that takes even better photos - but you're looking at a $6000 price-tag (versus ~$1400 for a 135mm).

That About Wraps It Up!

Now that was a bit of a winded article for how simple the answer was - but I thought it could only help to explain a little deeper than just a few simple words - but we sure answered your question, what does mm mean on a camera lens, right?! haha

If you have read this far - you're amazing - and it shows that you're serious about learning photography, different focal lengths, and everything in between. Good for you!

If you have any questions at all - feel free to drop us a line on either platform Facebook/Instagram.

Until next time folks, be safe and keep learning and creating!

Frequently Asked Questions

Is a higher mm lens better?

It depends entirely on your needs. A higher mm camera lens (narrower focal length) is great for reach (for sports, racing, etc.), and for portraits. Higher meaning at or above 50mm. But, if you're a landscape photographer, you wouldn't necessarily want a higher focal length because you want to capture more of your environment. Again, it all depends on what you need the lens for.

What MM is a normal lens?

That's a loaded question because there really isn't a 'normal' in the camera world. If you were asking what the most affordable, versatile, and (most likely) widely used camera lens/focal length... then that would probably go to the 50mm. 50mm is also regarded as 'about' the focal length that's seen through our eyes.

What does the 50MM mean?

50mm is the focal length of the camera lens. Specifically, the point of convergence (where all light comes to a point in your lens) is 50mm away from your sensor. a 50mm focal length is unique to itself (much like any other focal length). This is a very common focal length and is regarded by some as the most versatile focal length in all of photography/videography.

What does 300mm lens mean?

300mm is the focal length of the camera lens. Specifically, the point of convergence (the point in your lens where all waves of light come together) is 300mm away from your camera sensor. This is a telephoto lens and will give you quite a bit of reach for things such as sports, wildlife, events/concerts... basically anything you need that much of a reach for.

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