There are lots of numbers and letters on lenses, but what do they mean? It’s actually not that difficult to understand, so allow me to break it down for you.
This was another requested post from Barbara who’s on my video training course. When you’re on the course, you can make small requests like this.
Lets start with an easy one.
Numbers and Letters on Lenses
What does 18-55mm mean?
This refers to the focal length of your lens. 18mm is wide angle, and 55mm is more zoomed. When you zoom your lens in, you’re zooming between 18mm and 55mm. The ‘mm’ stands for millimeter, and this is the distance between your camera’s sensor, and the point of convergence in the lens. The further away the point of convergence is from the sensor, the more zoomed you will be.
This indicates the maximum aperture of your lens, which is how wide it will go, and ultimately how much light it will allow in. When the number is lower, it allows more light in.
Sometimes you will see lenses which say 1:2.8. This means that the lens will allow a maximum aperture of f/2.8 throughout the whole zoom range. When there is a hyphan, such as 3.5-5.6, this means that the more you zoom, the narrower the aperture will go. When you’re at 18mm, you maximum aperture will be f/3.5, but as you zoom, this aperture will slowly narrow, until you reach 55mm, at which point it will only allow and aperture of f/5.6.
The reason the number is a ratio (1:), is because aperture is measured as a ratio. You can learn all about aperture here.
I personally look for lenses which don’t change the aperture as I zoom, but these can be a lot more expensive.
What does Ø52mm mean?
That symbol of the circle with a line through it is the diameter symbol. In this case, it’s the diameter of the end of your lens (that’s the width of the lens for anyone who’s a little rusty on their math). This number is important to know for any lens caps or filters you buy for the lens, as you want to make sure you buy one which fits.
What does Macro 1:2 / 1:1 mean?
Technically speaking, your lens is a macro lens when the 1:1 ratio is displayed. It means that whatever you’re taking a photo of is going to be the same size on your camera sensor.
That said though, you will still often see Macro 1:2 listed. This isn’t technically macro, but it will be better than your standard lens, and you typically find this at longer focal lengths on a telephoto lens. It means that whatever you’re taking a photo of will be half it’s actual size on the camera’s sensor.
I remember an old telephoto lens I had, where I had to switch a button from normal focus to macro focus, which would also limit my zoom range too. So watch out for that.
What does HSM / USM mean?
They mean hypersonic motor and ultrasonic motor. They’re basically the same thing, named differently for different brands.
They’re silent wave motors which focus very quickly and quietly. This might not sound like much, but they have proven to be a real asset to me in the past.
What does II mean?
This means that it’s the second version of that particular lens. It’s quite common practice for lens manufacturors to take a very popular lens, and find away to improve it further, usually with better optics, and/or an image stabiliser. This means that they can sell it again, and make more money.
So when you see II on a lens, it’s the updated version of the lens, and this is probably the one you will want to buy.
What about the rest of those letters and numbers?
Here’s some information that I’ve taken from my lens buying guide. There more information in that article on the crop factor, and pro lenses, so check it out if that interests you.