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When youíre choosing a digital camera, the first thing to concentrate on is the lens furnished with it. You probably donít need to go into as much detail as Iím going to provide, but understanding the components of a camera lens does help you use your optics as much as it helps you choose them. The major things you need to know fall into four simple categories:
? The optical quality of the lens itself: Just how sharp is the piece of glass (or, these days, plastic)? The better the lens, the better it can capture ó resolve ó fine details. In most cases, the optical quality of digital camera lenses marches in lockstep with the price of the camera and the resolution of the sensor. Even at the low and medium ends of the price spectrum, digital cameras have good-quality lenses that usually can resolve a lot more detail than the 4- to 5-megapixel sensor can capture.
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Understanding How Lenses Work
Camera vendors have been mass-producing lenses like these for film cameras for decades, and any film camera can capture a lot more detail than an inexpensive digital camera. At higher price levels, lenses have better-quality optics, which are necessary to keep up with the detail-capturing capabilities of 6- to 8-megapixel (and higher) sensors.
? The amount of light the lens can transmit: Some lenses can capture larger amounts of light than others, generally because they have a greater diameter that can transmit more light. This factor, called lens speed, is a bit more complicated than that. Think of a 1-inch-diameter pipe and a 2-inch-diameter pipe and visualize how much more water (or light) the wider pipe can conduct; now youíre thinking in the right direction. Lens speed, in part, controls how low of a light level you can take pictures in. If you take many pictures in dim light, youíll want a faster lens. I look at this factor in greater detail later in this chapter.
? The focusing range of the lens: Some lenses can focus closer than others. The ability to get up-close and personal with your subject matter can be very important if your hobbies include things like stamp or coin collecting or if you want to take pictures of flowers or bugs. Indeed, close-focusing can open whole new worlds of photography for you, worlds you can explore in more detail in Book IV, Chapter 2.
? The magnification range of the lens: Virtually all digital cameras have a zoom lens, which allows you to vary the amount of magnification of the image. You might be able to take your basic image and double it in size (a 2:1 zoom ratio), triple it (a 3:1 zoom), or magnify it 12X or more
(a 12:1 zoom). The zoom range determines how much or how little of a particular subject you can include in an image from a particular shooting distance. As you might expect, the ability to zoom enhances your creative options significantly. At the widest settings (wide-angle settings), you can take in broad sweeps of landscape, whereas in the narrowest view (telephoto), you can reach out and bring a distant object much closer.
Understanding How Lenses Work
You donít need to have a degree in optical science to use a digital camera, but understanding how lens openings (f-stops) and some other components work can help you use those components more effectively.
Lenses consist of several optical elements made of glass or plastic that focus light in precise ways, much like you focus light with a magnifying glass or with a telescope or binoculars. The very simplest lenses, like those used on the least expensive digital cameras, are fixed focal length lenses, usually comprising just three or four pieces of glass. That is, the elements can produce an image only at a single magnification. You find these in the simplest point-and-shoot cameras that have no zooming capabilities. There arenít many of these around, but I did run into a camera with no ďrealĒ zoom recently: an
Understanding How Lenses Work 87
extra-compact model that used a 3:1 digital zoom as a substitute for optical zooming capabilities.
Most digital cameras have zoom lenses, which have very complex optical systems with 8, 10, 20, or more elements that move in precise ways to produce a continuous range of magnifications. Zoom lenses must be carefully designed to avoid bad things, such as stray beams of light that degrade the image bouncing around inside the lens. For that reason, when choosing a digital camera with a zoom lens, you need to pay attention to the quality of the image. All 4:1 zooms are not created equal; one vendor might produce an excellent lens with this range, whereas another might offer a lens that is less sharp. Among digital cameras with similar or identical sensors, lens quality can make the biggest difference in the final quality of an image. Youíll discover how to select the best lens for your needs as we go along.
You can get a top-quality lens and still save some money if you know how to interpret digital camera specifications. Many vendors share lenses and sensors among similar models in their product lines. I tested two cameras from the same manufacturer that had identical resolution and lens specifications, but one model was more compact, was outfitted with a rechargeable battery, and included rubber gaskets that made it water resistant. (It also cost $100 more!) A penny-pinching photographer who doesnít mind a tiny bit more bulk, is willing to use AA batteries, and doesnít plan any photography in rain showers could buy the less expensive version and save enough money to buy some extra memory cards or other accessories.