Lenses - Options & Uses

In photography a "normal lens" is a lens that generates images that retain a "natural" perspective and is roughly comparable to the human vision. Lenses of shorter focal length are called wide-angle lenses, while longer focal length lenses are called telephoto lenses.

For a 35 mm camera, the most commonly used normal lens is 50 mm, and anything with a focal length 35 mm or less is considered wide-angle. Common wide-angle lenses for a full-frame 35 mm camera are 35, 28, 24, 21, 18 and 14 mm. Wide-angle lenses come in both fixed-focal-length and zoom varieties.

In digital photography the situation is more complex. Most interchangeable-lens digital cameras are in the same form as 35 mm cameras, but have photosensors that are smaller than the image area of full-frame 35 mm cameras. This results in a narrower angle of view for any given focal length lens than would occur in a full-frame camera. On digital cameras lenses typically have a field of view that is the equivalent of a lens 1.6 times the focal length of the lens. The common 50 mm normal lens on a full-frame camera would have the field of view an 80 mm lens on a digital camera. A typical flexible zoom lens might be 28 - 80 mm on a full-frame camera. This would require an 18-55 mm digital lens (as comes standard on say, the Canon 300D) for an equivalent field of view.

A zoom lens allows the photographer to vary its focal length, as opposed to a prime lens, which has a fixed focal length. Zoom lenses are often described by the ratio of their longest to shortest focal lengths, eg. 100mm - 400mm may be described as a 4x zoom. Photographic zoom lenses should not be confused with telephoto lenses, those with narrow angles of view that bring the subject in closer. Some zoom lenses are telephoto, some are wide-angle, and others cover a range from wide-angle to telephoto. Lenses in the latter group of zoom lenses, sometimes referred to as "normal" zooms, have displaced the fixed prime lens as the popular one-lens selection on many contemporary cameras.

Wide-angle lenses are ideal for scenery photos, especially in the Australian outback where the landscapes are often vast and widespread. Often, the better quality Digital SLR (D-SLR) cameras will include a kit zoom lens (for instance 18–55 mm) which is ideal as the short focal length is provides a wide field of view for all but the most panoramic of scenes, and the long focal length is sufficient for portrait photography. This range will limit your ability to zoom in close on very long distance shots, so the additional purchase of lens to about 200 mm would give you the ability to zoom in tight on a small item in the distance (see Telephoto and Zoom section).

Life gets more interesting when you can get a 1:1 image size or closer. Photos of tiny details such as eyes on a fly, aphids on the petal of a flower, or reflections in a droplet of water are all examples of things that can only be photographed using a macro lens.

In all photography (including macro), as the lens gets closer to the subject , the image gets larger on the film (or image sensor) so the light reaching the sensor is lessened. The depth of field also becomes very shallow and to combat this, very small apertures are called for, which lessens the light even more. Both these things in combination mean that normal handheld exposures are usually out of the question. A tripod is needed for steadiness plus flash or reflector is needed in nearly every circumstance to give decent illumination.

Compact digital cameras often have a macro mode that lets you get close to the subject and get a good image but they usually end up with the lens very close to the subject, which is fine for flowers and static objects but can annoy insects and alter their behaviour and narrow depth of field is often an insurmountable issue.

In compact cameras look for the “macro” mode (usually a tulip symbol) and maybe also a “super macro” mode (tulip plus a ‘s’ is one way to show it). Often the flash is automatically disabled on compact digital cameras when working at the “super macro” distances, as the subject is too close for proper coverage. Make sure you have some other means of lighting in that case. Some digital cameras allow the in-body flash to be set at lower output in order to still trigger the slave flash but not produce too much light from the position of the camera.

Remember that aluminium foil, styro-foam and other bright surfaces make good and inexpensive reflectors.

There's another little trick with digital cameras and closeups. If you take your photo using the camera's highest resolution setting (to maximise file size), and go in as close as your lens (and light) will allow, you can get the illusion of enlargement by cropping the picture on your computer (with image software) to create a full frame picture of the subject that retains sufficient quality suitable for printing a 6"x4" or for email/web use.

If you're serious about macro photography, you'll probably need to invest in specialised lenses, adaptors, ring-flashes and slaves.

Capturing animals such as birds in flight, or small marsupials is every photographers delight. However the photographer's success lies much in their use of specialised equipment. Most wildlife will move before the photographer can get in close enough for the ideal frame so investing in a powerful zoom lens if required.

When purchasing a lens, the cheaper models will offer the focal length but not the aperture range, which will limit the speed you can shoot from a distance, or in lower light. For outback wildlife photography, you would spend money wisely on the best quality zoom lens your budget can afford.