Focal length is the distance from the lens center to the image sensor (focal plane). Each lens has its own unique focal‑length value.

Focal length is a critical parameter, as it determines the field‑of‑view, or how much of a scene can be captured. As illustrated below: the shorter the focal length, the wider the shooting coverage; the longer the focal length, the larger distant objects will appear in the frame.

Note: The relationship between focal length and field‑of‑view varies across cameras. Unless otherwise specified, this shooting guide references APS‑C format cameras.

Generally speaking, a lens with around 35 mm focal length is regarded as a standard lens, whose field‑of‑view approximates human vision. Lenses with shorter focal lengths are wide‑angle lenses, while those with longer focal lengths are telephoto lenses. These categories have no rigid dividing criteria. Select different lenses according to your subject and desired image outcome.

Now take a look at your lens. Its available focal‑length range is printed on the lens barrel. For instance, the SAL55200‑2 shown below supports focal lengths from 55 mm to 200 mm. Marks for the currently set focal length can be found on the mount‑side of the lens barrel (near the camera body). In the example below, the current focal length is 55 mm.

In this illustration, “55‑200” on the left denotes the lens’ available focal‑length range. The white indicator line on the right points to the active focal‑length setting.

Zoom Lenses vs Prime Lenses

Lenses fall into two categories: zoom lenses with variable focal length, and prime lenses with fixed focal length. Certain zoom lenses cover ranges from wide‑angle to telephoto, supporting diverse shooting scenarios. They are highly practical for everyday shooting and especially convenient for travel. When you prefer travelling light, they reduce the number of accessories you need to carry.

By contrast, with a prime lens that offers no zoom capability, you adjust composition by physically moving your position. Nevertheless, prime lenses generally deliver faster performance with larger apertures. They are ideal for heavy background bokeh effects, or for achieving faster shutter speeds to suppress motion blur under low‑light conditions. Moreover, they deliver superior imaging performance, yielding image quality difficult to attain with zoom lenses.

This sample image was captured with a prime lens. When the aperture is set to a small F‑number, the background exhibits strong bokeh.

Macro lenses used for close‑up subject shooting are also prime lenses. Although many modern zoom lenses feature macro capability with short minimum focusing distances, their performance still cannot match dedicated macro lenses.

This photograph captures fine sunflower details taken with a macro lens. Macro lenses allow you to get much closer to your subject.