What Do The Numbers And Letters On My Lens Mean

What Do The Numbers And Letters On My Lens Mean?

How many times you looked at your lens and asked yourself this question: What do the numbers and letters on my lens mean?

In this post I’ll explain what they mean but you still need to know the basics of photography to realize if the lens in your hand is what you need or not. Let me rephrase that sentence: reading those numbers and letters on lenses without the basic knowledge of photography is like being able to read words of foreign language but not really understanding what they mean – I can read Cyrillic letters but I don’t understand 99.99% of the words that I read.

We will be using a photo of  a canon lens’ front, however the explanation can be applied on almost any lens brand in the market.

1- EF-M

This stands for the lens mount. EF is used for canon lenses while DX is used for Nikon. M stands for Canon EOS M mirrorless camera. EF-S on Canon lens means it is for cropped frame cameras and EF is for full frame. EF lenses can be used on cropped frame cameras but EF-S lenses can not work on full frame cameras.

2- 11-22 mm

This is the focal length of your lens. 11mm is the closest distance between camera sensor and the lens’s point of convergence, while the 22mm is furthest distance. The shorter the distance between the sensor and the convergence point the wider is the angle of view of the lens, while the larger the distance the more zoomed the camera is, example 300mm lens is a super zoom lens.

lens focal length

3- 1:4-5.6

This refers to the maximum aperture size of your lens at the two extremes of the focal length. In this example, at 11mm, the aperture maximum opening will be f 4 and at 22mm it will be f 5.6. The aperture is responsible for controlling the amount of light entering the lens. The smaller the aperture number is, the wider its size, and the more light is entering. The larger the aperture number is, the smaller its size, and the less light is entering.


On more expensive lenses you will see something like 1:2.8, only one aperture value and no hyphen. This means that the lens will have a maximum aperture value of f/2.8 throughout the zoom range.

4- IS

This stands for Image Stabilizer. It is a technology in the lens to help you reduce the blurriness in your photos due to camera movement. You might find IS II and that stands for 2nd generation image stabilizer technology. This is useful for lenses with longer focal length such as super zoom lenses. Please note that not all lenses have IS.

5- STM

It describes the motor of the lens. Different lenses will have different letters describing the different options or technologies they have such as their silent motors or the lens zooms that extends during zooming or not, etc.

Such information can be obtained from the lens booklet that comes with it or ask the sales personnel in the shop.

6- 55mm

The number that comes after the symbol of circle with line passing through it is the lens’s diameter. This is important if you want to buy a lens cap or a lens filter as you need to make sure you buy the right one.

I’m sure this post will give you a better understanding of all these numbers and letters on the lenses that you are going to look at from now on.

If you have any questions about this post, lenses, or photography, then please feel free to contact me in the comments section below, on social media, or by emailing me on

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