The zoom lens has both advantages and disadvantages.
With the variety of lenses out there for both film and digital cameras, figuring out what you need can be a dizzying experience. Some lenses are good for a variety of situations, while others can be advantageous or even detrimental in certain situations. The lighting, amount of action and distance to the subject are a few considerations when deciding what camera lens to use.
Long Lenses
Long lenses on a 35mm camera measure anywhere from 70mm to 300mm, or even longer. They are mostly used to "zoom in" on a subject that is far away. They are also a common choice for portrait photographers. Long lenses are used at a medium to far distance from the subject to avoid any chance of facial feature distortion that can occur with a shorter lens.
Wide Angle, or Short Lenses
Wide angle lenses can measure anywhere between 40mm and 20mm. Any shorter than this, the lens exhibits "fisheye" distortion. Wide angle lenses are good for landscapes and photographing in areas where you cannot back up. However, wide angle lenses are bad for architecture, as they curve straight lines. Because they tend to enlarge whatever is closest to the lens, they are not recommended for portraiture, since they increase the size of noses and chins.
Long Lenses and Shutter Speeds
Extremely long lenses can be difficult to keep still, resulting in blurred photos. When using a "normal" 50mm lens, it is widely taught that using a shutter speed of 1/30 of a second or slower can result in a blurred image from simply hand-holding the camera. The rule is to take the focal length of your lens, place the number into a fraction, and look to the next-lowest shutter speed for your guide. For example, if you are using a 300mm lens, turn it into 1/300, and skip to the next-slower standard shutter speed, which is 1/250 of a second. This means you may experience blur in your image at 1/250 or slower, and should use a tripod.
Focal Length and Depth of Field
Depth of field, or aperture, changes according to whether you are using a long or short lens. An aperture setting of f/8, which is average, will appear more shallow on a long lens than it will on a short lens. Often in portraiture, it is desirable to blur the background, which makes long lenses and their inherent shallow depth of field desirable. Conversely, landscapes often look better when completely sharp, so wide-angle lenses with their wider depth of field work well.
Zoom Lenses vs. Fixed Lenses
Zoom lenses, with their variety of focal lengths, often seem like the obvious choice over using a fixed focal length lens. However, if you find yourself needing a "fast" lens, a fixed lens offers advantages. When a lens opens up to a very wide depth of field, such as f/1.4, it is called a fast lens because it allows the use of faster shutter speeds. Most zoom lenses will not be as fast as its fixed counterpart. For example, a 28mm to 80mm zoom lens may open up as wide as f/3.5, but a fixed 28mm lens can open up even wider. Fast zoom lenses are available, but they are more expensive than their standard counterparts.
Tags: angle lenses, depth field, shutter speed, fast lens, focal length, lens open, lenses good