Focal length

Alpha Tutorial :4 - Focal length

Focal length is the distance from the centre of the lens to the image sensor (focal plane), and each lens has a different focal length. Focal length is important since it determines the range of a scene you can capture (angle of view). As shown in the following photographs, the shorter the focal length is, the wider the range you can capture, while the longer the focal length is, the more distant objects appear larger.

(*) The relationship between focal length and angle of view varies depending on cameras. The explanation in this Shooting Guide is based on APS-C format cameras, unless specified otherwise.

Focal length 11mm

11 mm

Focal length 16mm

16 mm

Focal length 23mm

23 mm

Focal length 33mm

33 mm

Focal length 57mm

57 mm

Focal length 90mm

90 mm

Focal length 200mm

200 mm

Focal length 330mm

330 mm

Generally, lenses with a focal length of around 35 mm are called "normal lenses" as they have an angle of view close to the human visual field. Lenses with a focal length shorter than this are called "wide-angle lenses," and those with a longer focal length are called "telephoto lenses." However, there are no strict standards for these terms. Use different lenses according to subjects or images you want to shoot.

shot with focal length

Let's check the focal length of your lens. The range of the focal length available with the lens is printed on the lens. For example, the focal lengths from 55 mm to 200 mm are available with SAL55200-2 in the picture below. Also, on the mount side of the lens barrel (near the camera body), you can see the mark for the focal length currently set. In the picture below, the current focal length is 55 mm.

55-200 lens

In this picture, "55-200" on the left side is the range of the focal length available with the lens. The white line on the right side indicates the focal length currently set.

Types of Lenses

Wide-angle Lenses

Wide-angle lenses have shorter focal lengths, usually 24mm and below. Because they have a wider angle of view, wide-angle lenses can capture more of a scene than lenses with longer focal lengths, making them ideal for shooting in enclosed spaces or capturing a lot in a single image.

But wide-angle lenses also exaggerate perspectives, which can distort the way an image looks. They also make subjects appear further away from each other than they are in reality.

Wide-angle Lenses 11 and 18mmWide-angle Lenses 24 and 28mm

Normal Lenses

A focal length of 50mm provides an angle of view similar to what the human eye sees, so this focal length is associated with the normal or standard lens. What you see has minimal distortion, unlike wide-angle lenses which exaggerate perspective and telephoto lenses which compress perspective. Standard zoom lenses also refer to lenses which have focal lengths somewhere in-between wide-angle and telephoto lenses.

Normal Lenses

Telephoto Lenses

Usually in the range of 70 to 300mm, telephoto lenses are used to magnify subjects far away. With a smaller angle of view as compared to wider lenses, telephoto lenses tend to compress perspective and make subjects look close together.

Telephoto lenses are usually used when photographers have to shoot from far away, like during sports and wildlife photography, but lengths like 85mm are also popular among portrait photographers because of the slight compression on perspective, which makes a person’s features look more natural.

Telephoto Lenses 70 and 100mm

Super Telephoto Lenses

Super telephoto lenses have an immense zoom range which can go from 400mm all the way to 2000mm. These kinds of lenses are used for shoots with very distant subjects like wildlife and astronomy. DSLR super telephoto lenses can be massive and need to be mounted on a tripod or monopod, but there are smaller super telephoto lenses for mirrorless system cameras which are more compact.

Super Telephoto Lenses

Specialty Lenses

Fisheye Lenses

Fisheye lenses are wide-angle lenses which can reach angles of view close to or at 180 degrees. They provide an extreme angle of view which encompasses almost everything you can see in a scene – sometimes even your own feet as you’re holding the camera! But fisheye lenses also distort the image, making everything twist as if stretched onto a globe.

This was shot with a Sony Alpha 16mm F2.8 Fisheye lens, which gives you the distinctive fishbowl look.

This was shot with a Sony Alpha 16mm F2.8 Fisheye lens, which gives you the distinctive fishbowl look.

Macro Lenses

Macro lenses magnify subjects which are very small and/or very close. Most compact cameras have a macro mode, as do some interchangeable lenses. But true macro lenses provide you with more advantages; for one you can get 1:1 reproduction which means that a 10cm subject will be reproduced through the glass as 10cm on your sensor. They also let you get closer to a subject and still achieve focus.

This was shot with the E 30mm F3.5 Macro lens, which lets you get really close to your subjects.

This was shot with the E 30mm F3.5 Macro lens, which lets you get really close to your subjects.

Tilt-Shift Lenses

One of the problems with shooting with wide-angle lenses is how perspectives distort, for example, if you photograph a tall building the vertical lines will converge to a point. Tilt-shift, or perspective control lenses, let you control the appearance of perspective in an image so that you can maintain those straight lines and produce a more accurate photo without distortion.

Tilt-shift lenses can also manipulate the depth of field in a unique way. With a regular lens, the depth of field is perpendicular – subjects appear sharp and out of focus in planes of focus perpendicular to the lens according to their distance.

With tilt-shift lenses’ ability to focus selectively, the plane of focus can be tilted to almost parallel to the camera, so that parts of the scene at varying distances from the camera can still be rendered sharply.

Let's check the focal length of your lens. The range of the focal length available with the lens is printed on the lens. For example, the focal lengths from 55 mm to 200 mm are available with SAL55200-2 in the picture below.

Also, on the mount side of the lens barrel (near the camera body), you can see the mark for the focal length currently set. In the picture below, the current focal length is 55 mm.

In this picture,

In this picture, "55-200" on the left side is the range of the focal length available with the lens. The white line on the right side indicates the focal length currently set.