Types Of Camera Lenses
A description of various camera lenses and their uses. Standard, Telephoto, and Wide Angle lenses as well as zoom and telephoto converter capabilities.
Many photographers have and use only one camera but often use many different lenses. These lenses increase the flexibility of a camera and allow for more creative pictures. The wide range of lenses that are available can sometimes overwhelm beginners. However, most lenses are not too difficult to understand and use. There are three basic types of lenses, Standard, Telephoto, and Wide Angle. There are also special features and converters that can be used in conjunction with these lenses for added range.
Standard lenses have a focal length that is equal in distance to the diagonal of the negative. This distance for 35mm film is generally 45mm and for single lens reflex lenses it is anywhere from 445-55mm. Standard lenses have the unusual quality of reproducing an image exactly as it appears. These lenses are typically seen as a default lens and do not offer telephoto or wide-angle capabilities. They are also less expensive than lenses with added properties and make excellent basic lenses.
A Telephoto lens has a focal length that is longer than 55mm but typically starts out at 70mm. This lens allows you to bring the subject closer to you and/or crop out any unwanted background or obstructions. A short telephoto lens, such as a 70mm, will allow you to take excellent portraits. It will let you take good head and shoulder shots without moving in close to your model, which may make him/her feel uncomfortable. A longer lens, such as a 210mm or 300mm, will let you see further so you can photograph boats, planes, or wild animals from a distance. There are two important limitations to remember when using telephoto lenses. They tend to shorten your depth of focus and they are more susceptible to camera shake. A standard lens may have 10-12 feet of depth in focus while a telephoto lens may be limited to 3-4 feet. Camera shake is a result of noticeable movement of the camera that is seen on the film. It generally appears when the shutter speed is set too low but can usually be compensated for. To correct this problem, use a shutter speed equal to or faster than 1/(focal length). For example, when using a 210mm lens, you should set the shutter speed at 1/250 second.
Wide-Angle lenses widen the angle of view from the camera. Typically lenses with focal lengths of 40mm or less are considered wide-angle lenses and lenses with less than 18mm focal lengths are usually considered to be ultra-wide-angle lenses. These lenses allow you to expand the scope of your photograph without having to move back in order to get everything you want to see in the frame. They are very useful when taking photographs inside when you may not be able to back up or with landscapes where your positioning will not significantly alter the angle of your photograph. Since lenses with focal lengths of 30mm or less have a tendency to distort the edges of your photograph, wide-angle and ultra-wide angle lenses can be used to create special effects. Anything that is close to the lens will appear disproportionately large in comparison to the rest of the picture. To get a similar effect, try looking at yourself through the back of a spoon. Wide-angle lenses have a long depth of field and should be considered when selective focus is desired in your photographs.
Lenses that feature zoom capabilities do not have a fixed focal length. This can be a benefit because you can use one lens for a wider range of shots. For example, if you purchase a 70-210 lens you can take pictures within this range by dialing in the zoom to where you would like the lens set rather than changing the lens each time you want a different focal length. This is an essential feature when shooting action or wildlife shots where time is of the essence and there is no time to keep changing lenses. The main drawback to the zoom feature relates directly to the lense's ability to change focal lengths. A zoom lens must have a smaller aperture than a standard lens with a fixed focal length. Therefore, you must use longer shutter speeds and have less flexibility with your photographs. It is also advisable that you use a tripod with a zoom or telephoto zoom lens to avoid having camera shake.
Tele-extenders or telephoto converters are tubes that mount onto the camera and then allow you to mount the lens to the converter. The purpose of this is to extend the focal length of your camera. They are available in several varieties but the 2x and 3x are the most popular. The 2x will double the focal length of the lens. Converters are less expensive than buying lenses with the same focal length that the converter can provide however, there are many drawbacks when using them. Converters will reduce the quality of you photographs and cause them to loose sharpness, contrast and color vibrancy when compared to normal lenses. You will need to use longer shutter speeds as well since the converters will reduce your overall aperture by 2 or 3 f-stops and may result in longer focal lengths. They may also interfere with the normal functions of your camera such as the auto focus, shutter speed, and aperture settings or programs.