Camera lenses can be divided into three main categories: wide-angle, standard, and telephoto (long-focus). However, since focal length is determined by the camera's format, it is not easy to define the exact focal length range for each category. The focal length of a standard lens is roughly equal to the diagonal of the image frame. For a 35mm camera, the film diagonal is about 50mm, so lenses with a focal length of 50–55mm are considered standard lenses, while an 80mm lens is considered a medium telephoto lens. For 6×6cm film, the diagonal is about 80mm, making an 80mm lens a standard lens for medium-format cameras. When shooting the same scene with a 35mm camera and a medium-format camera both equipped with standard lenses, the subjects appear in roughly the same proportions, although the film sizes are often different.

Standard Lens

The standard lens for a 30mm format has a focal length of 50mm; a typical wide-angle lens has a focal length of 28mm; a typical telephoto lens has a focal length of 80mm. Images taken with a standard lens closely resemble what we see with the naked eye. Most 35mm single-lens reflex cameras come with a standard lens, but lenses with shorter or longer focal lengths can also be used. Standard lenses usually have a relatively large maximum aperture, making them suitable for low-light conditions. They are ideal for photographing most outdoor scenes.

Wide-Angle Lens: A wide-angle lens has a wider field of view than a standard lens, making it suitable for group portraits or photography in confined spaces. If you get too close to your subject, image distortion may occur. Regardless of the aperture setting, the depth of field is generally larger, which is very useful when you need every part of the subject to be sharply in focus. Wide-angle lenses are well suited for indoor photography.

Zoom Lens: A zoom lens allows you to precisely adjust the framing of your subject by varying the focal length. Each zoom lens covers the focal length range of three or four fixed-focal-length lenses, offering great flexibility for cost-effective shooting. Since you don’t need to change lenses, you’re less likely to miss important moments. Zoom lenses are ideal for capturing dynamic scenes.

Telephoto Lens: Telephoto lenses are very useful when photographing distant subjects or large images, or when you cannot get close to the subject with a shorter lens. Due to their heavier weight, using a faster shutter speed to avoid camera shake is more critical with telephoto lenses than with lighter, shorter lenses. A telephoto lens is a compact, relatively short-length version of a long-focus lens. Telephoto lenses are suitable for photographing natural history subjects.