You may notice camera lenses are described by one or two numbers, most often in millimetres, like 14mm or 18-55mm. As a new photographer, you may have no idea what these figures mean because photo websites and product descriptions often list them without explanation. These numbers are essential to know. Once you understand what they are and what they mean for your shots, you can better choose the right lens for the variety of scenes you tend to shoot.
These numbers you see on every lens represent that lens’ focal length. It is the measurement between your lens and your camera’s image sensor. If your lens is fixed-length, or prime, then it always rests at the same distance from your sensor, so its length is just one number. If your lens has the capacity to zoom, then it has two stats for both the minimum and maximum distance it sits from your camera’s sensor.
This distance tells you not only about the physical attributes of the lens but also the type of shots it creates. A lower focal length means a wider field of view, or a greater angle of what the lens can perceive in focus. The Fujifilm XF14mmF2.8, for example, is a prime lens that shoots at an 89-degree angle, with high resolution from the centre to the periphery of the frame. Compare that with the XF100-400mmF4.5-5.6, a super telephoto lens that ranges from 16 to 4 degrees in its field of view. With that latter type of lens, you abandon the wide angle to highlight a closer, more specific segment of what the unaided eye can see.
If you are a new photographer, then you are likely shooting with just one or two lenses. There are great mid-range lenses that work for several situations, including personal use moments, like candid shots of family or friends. The XF18-55mmF2.8-4 is one such option with a broad focal range that spans 79 to 28 degrees, depending on the zoom. That type of mid-length lens with zoom is a great choice for starting your creative endeavour and for shooting as you travel with light cargo.
As you develop your craft, you may wish to utilise lenses designed for specific photo opportunities. If you shoot landscape and architecture photos, then you want a lens with a low focal length, between 14 and 18mm, for its wide angle. For your full-body portraits, you should look at a lens with a mid-range focal length between 23mm and 50mm. When dealing with moving or distant photo subjects, you should choose a zoom lens with a focal length of 200mm or more.
By knowing the difference between lens focal lengths, you can experiment with more lenses and be confident that you know which lens to grab in every situation.