Types of Lenses
Lenses are generally categorized as zoom, interchangeable, integrated, and macro. Zoom lenses are the most expensive, offering a range of focal lengths. Interchangeable lenses usually fit on expensive DSLRs and can be either zoom or a fixed focal length. Integrated lenses are part of the camera and cannot be switched out. Macro lenses are specialty lenses for close-up work.
A zoom lens has a variable focal length, meaning it allows you to adjust the focal length over a variety of ranges. The range of focal lengths a zoom lens covers usually is specified by its magnification. For instance, a 3″ zoom lens will enlarge or reduce the subject in an image by three times.
Zoom lenses are optical or digital or both. An optical zoom lens truly changes the amount of the subject falling on the image sensor. This results in every pixel in the image containing unique data, providing a final photo that is crisp and clear. The advantage of an optical zoom is its ability to take more detailed pictures of faraway objects. An optical zoom's magnification level is measured in degrees, such as 3″ or 10″.
A 2″ optical zoom means that if the camera's minimum focal length is 50 mm, the lens has the ability to take photos up to 100 mm.
Because of the nature of optics, the maximum aperture (f-stop) of a zoom lens will be different from one end of the zoom range to the other. The lower zoom range will allow a greater aperture opening and the telephoto range will lead to a smaller maximum aperture.
A digital zoom takes a part of the normal image and enlarges it to give the appearance that you have zoomed in on the subject. The digital zoom adds new pixels to the image using interpolation software. Many cameras have an optical zoom combined with a digital zoom that only kicks in after the optical zoom has reached its maximum point. If you are given a choice, you should always choose the optical zoom over the digital zoom. The digital zoom lens is not really zooming. By enlarging part of the image with software it is only giving the appearance of having zoomed in on the subject. With an optical zoom, you are varying the focal length. When you zoom in, the focal length increases. When you zoom out, the focal length decreases.
High-end DSLR cameras allow lenses to be changed on the camera body. An interchangeable lens can be detached from the camera and replaced with another lens having the same type of mount. Professional photographers rely on interchangeable lenses to create desired effects depending on the situation they are shooting. If you are considering purchasing a digital camera with an interchangeable lens, be sure to investigate the number and types of lenses that are available.
An integrated lens is part of the camera and is not detachable. Some integrated lenses allow you to add supplementary lenses. Typically, supplementary lenses screw onto the lens barrel thread or slip over it with a friction mount. A supplementary lens changes the viewing angle of the lens or allows it to focus more closely than it would in macro mode. Many integrated lenses are zoom lenses.
Some digital cameras can focus as close as one or two inches (or even closer) from the subject. This capability will be appreciated by the nature photographer hoping to catch the opening buds of wild orchids in the spring or tiny crabs scampering down a beach. A macro lens can come in handy even around your own home. With a macro lens on your digicam, getting down on your knees for a close-up shot of your new kitten can provide delightful results. See the color pages for macro shots of agate, soap bubbles, flowers, and leaves.
While there are dedicated macro lenses, many cameras with zoom lenses now have a macro setting. Typically the camera must be zoomed back to the shortest focal length and then a button pushed to go into macro mode. Some noninterchangeable lens cameras also have a macro mode. Check your camera's manual for specifics.
Since DSLR cameras allow changing lenses, you can buy a lens just for macro photography. There are even telephoto macro lenses that allow the photographer more working distance, which can be important in extreme close-up photography.
Looking closely at ordinary things, such as this embroidery, reveals a world of picture possibilities.