The following lenses are the most common you will find on the market for amateur and professional use. You may want to add to your existing lens kit some time; following are lens definitions and major options to consider when researching.
Telephoto Lenses (200m, 500mm, 1000mm)
Telephoto lenses or long focus lenses produce larger images of distant subjects than shorter focal length lenses or normal lenses. They require extra extension to place them further from the film plane. The greater the extension or focal length of the lens the greater the magnification.
This extension presents no problem with a stand camera but does with portable or hand held cameras. The lenses are long and bulky, they are unbalanced and awkward to use in the hand and it is virtually impossible to eliminate hand shake and movement from shutter release.
The telephoto lens gives a very shallow depth-of-field and is often not corrected for subjects closer than 5 to 10 metres. It is therefore excellent for picking out distant, virtually perspective less detail, and de-emphasising surroundings. The telephoto has the ability to compress scenes.
Tele-converters, an extension tube containing optical components are made for use between lenses and body. They are cheaper than telephoto lenses but image quality is generally poor. The most common telephoto lens is around the 200mm size, and of course, the cheapest.
Wide Angle Lenses (18mm, 20mm, 28mm, 35mm)
A wide angle lens or short focal length lens produces smaller images and wider views than the longer focal length lenses or normal lenses.
Problems with wide angle lenses are perspective distortions and are gross at close lens to subject's distances. Lines will converge and diverge and close subjects are size disproportionate.
In addition, because of the wide angle of view you are prone to aberrations in strong lighting conditions. Most wide angle lenses are supplied with lens hoods to help overcome acute light rays. Such aberrations include lens flare and corner fall off.
Wide angle lenses are useful when close camera to subject distance and maximum depth-of-field is required. The 28mm is generally what most people choose,and the wider you go the more expensive. The most expensive is the following lens, the fish eye.
Fish Eye Lenses (6mm 220o, 14mm 180o)
The fish eye lens sacrifices correction of linear distortion in favour of extreme angle of view. Depth-of-field is extensive and definition quite good. Some fish eyes have been produced for scientific purposes, such as total sky photography for meteorology. Mostly they are used to give spectacular distortions in commercial images.
High cost and limited applications mean that these lenses are usually hired and not purchased.
Macro Lenses
Macro is a general term applied to lenses for close-up photography - conditions where the image is larger than the subject. They are generally of short focus and corrected for close subject distance.
The use of macro lenses at their smallest aperture should be avoided. The very high effective f/ can lead to image deterioration due to refraction.
Bellows and extensions tubes are available to extend the range of the macro lens. Macro lenses are also an expensive lens, so chooses carefully.
Zoom Lenses (80-220mm, 35-120mm)
Zoom lenses combine the basic forms of several lenses in a single lens. For a lens to accomplish this calls for a complex optical system comprising many elements. Zoom lenses are generally acquired to replace a large range of lenses and are particularly useful for travel.
Zoom lenses are generally in the longer focal length which presents the problem associated with this focal range. Also because of the additional elements in the design of the lens, quality suffers.
This lens is the most popular these days and are usually offrered as part of the kit when you purchase a camera. As this is a common lens, it is quite cheap, however, like telephoto lenses, the longer the lens the more expensive.
Soft Focus Lenses (120mm portrait lens)
A soft focus lens represents a point of light as a circular patch of light with a core of greater intensity. It therefore differs from an out-of-focus image. The effect is a luminous halo or softness of outline.
Soft focus lenses are usually of high quality and have history of use in portraiture, fashion, glamour and more recently in boudoir photography.
Soft focus can also be achieved through soft focus filters. These lenses are very expensive and usually purchased by professional photographers who are doing a lot of glamour and fashion work with models.
Process Lenses
Process or copying lenses are specifically designed for copying work. It is essential for such lenses to have an undistorted field of view (flat), even illumination and a high degree of chromatic correction.
Process lenses are not required to cover a wide field and need not be of wide aperture. Maximum aperture is frequently f/8 and the field of view is normally a 1:1 ratio.
Mirror Lenses (500mm, 1000mm)
The mirror differs from all the above as it is a reflecting system and not optical. Mirror lenses are recognised by their characteristic drum shape and the opaque central area of the front element.
Mirror lenses are popular for long focal lengths for small cameras as they are considerably shorter than their optical counterparts. Mirror lenses are also cheaper than long optical lenses.
Problems are that these lenses suffer from aberrations and cannot focus to close subjects (1000mm min 30m) and lens speed is slow (f/10.5)
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