Types of Camera Lenses

Purchasing a Single Lens Reflex (SLR) camera gives the photographer the advantage of choosing among different lenses and the ability to change those lenses. The choices seem endless, though, and it is sometimes difficult to determine which additional lenses to buy.

Here's a run-down of the most common lenses and some of the specialty lenses for an SLR camera.

The three basic lens types, determined by the focal length (measured in millimeters) of the lenses, are the following:

• Normal. A normal lens shows most accurately what a normal human eye will see. 50mm is a typical normal focal length. The 50mm is the most popular and versatile lens. The quality is excellent while also being inexpensive. It is smaller and lighter, and the aperture allows photographs to be taken in low-light situations.
  
  
  
  
  
  
• Telephoto. A telephone lens brings the background closer. Longer-than-normal focal lengths such as 70mm and 300mm are typical for a telephoto lens. Since a telephoto lens will bring the subject up close, it is popular for sports photography.
  
  
  
  
  
  
• Wide. A wide lens captures a wider expanse of the background than what the human eye will see. Shorter-than-normal focal lengths such as 24mm and 35 mm are typical for a wide lens. Wide lenses are popular for landscape photography and large group shots.

Lenses come in either prime or zoom. Prime lenses have a fixed focal length. In order to fit more or less into the viewfinder, the photographer must physically move forward or backward. Focal length in a zoom lens can be changed by turning the zoom ring on the lens. A zoom will have a variable focal length such as 28mm-105mm. While zoom lenses are more convenient for storage and versatility, prime lenses often have a sharper lens and work better in low-light situations.

In addition to focal length, consider the lens speed and its focusing distance. The lens speed is determined by the f-stop setting. A faster lens will be heavier and more expensive. The focusing distance is the distance from the lens to the subject needed to achieve a focused photograph.

Other special lenses to consider include the following:

• Macro. A macro lens's focus is closer to the subject and is used for close-up photography.
• Fisheye. A fisheye lens uses an angle of view up to 180 degrees. The angle distorts the photograph so the four sides appear to be farther away.
• Teleconverter. A teleconverter attaches between the camera and another lens. It increases the focal length of your lens. Although teleconverters will bring the subject closer, they do not allow as much light through the lens. Thus, they need slower shutter speeds and/or a fast ISO.

Digital camera SLR users need to be aware of the focal length differences in lenses that are interchangeable for film and digital cameras. All focal lengths listed on interchangeable lenses are for film cameras. To get the true focal length of a digital camera the number needs to be multiplied by 1.6. Remember that the lens won't be as wide on a digital camera as you would get on a film camera using the same lens. For example, the standard 50mm lens on a film camera is actually 80mm on a digital camera.

When purchasing a new lens, first consider your needs. What will you be photographing? The subjects of your photographs should dictate whether you need a normal, telephoto or wide lens. Then, consider the trade-off between the optics quality, the camera's weight, the convenience of a prime vs. a zoom lens, lens speed, focal distance and price. Often it will be a balance of these considerations that leads you to a good camera.