Among the most essential part of a digital SLR is the lens- or, more properly, lenses, because, unlike other types of digital cameras, which might utilize add-on lens adapters, the lens of a DSLR is totally interchangeable. I’m not going to inform you much about how lenses work. The majority of the rest of this area will handle useful matters connecting to interchangeable lenses on a DSLR. The only things you truly need to understand about lenses are these:

■ Lenses consist of precision-crafted pieces of optical glass (or plastic or ceramic product) called aspects, organized into groups that are moved together to alter the magnification or focus. The components may be based upon pieces of spheres, or not (in which case they are aspherical), and provided special finishes to decrease or get rid of undesirable reflections.

■ Lenses include an iris-like opening called a diaphragm that can be changed in size to admit basically light to the sensing unit. In addition to adjusting the amount of light that passes through the lens, the diaphragm and its shape impact things like relative overall sharpness of an image, the amount of an image that remains in focus, the brightness of your view through the viewfinder, and even the shape and qualities of out-of-focus highlights in your image. I’ll describe these elements in more information as they show up.

■ Lenses are installed in a real estate that keeps the aspects from rattling around and supplies a method to move them to change focus and magnification. The lens housing can include a microprocessor, a small motor for changing the focus (and, in non-DSLR electronic cameras, for zooming), and maybe a mechanism for reducing the effects of cam shake (called vibration reduction). Included are threads or a bayonet mount for attaching filters, a fitting that connects to your electronic camera, and different levers and electronic contacts for interacting with the cam body. You might find a switch or two for changing from autofocus to manual focus, locking a zoom lens so it doesn’t extend mistakenly while the cam is being carried, and a macro, lock/lockout button to restrict the looking for range of your autofocus mechanism so your lens won’t seek focus from infinity to a few inches away whenever you partly depress the shutter release. Everything else is details, and we’ll take a look at them in this and later chapters of this book. Lens Interchangeability The ability to remove a lens and swap it for another is one of the crucial advantages of the digital SLR. Interchangeable lenses make a very cool tool because they broaden the professional photographer’s flexibility in several ways:

■ Swapping lenses lets you alter the “reach” of a lens, from wide-angle to medium telephoto to long telephoto. The zoom lenses on non-SLR cameras offer some of this flexibility, but they can’t provide the zoom of the longest telephotos and telephoto zooms, nor the wide-angle point of view of the quickest focal lengths discovered in some interchangeable lenses and zooms

■ Interchangeable lenses let you pick a lens optimized for a particular function. Do everything zooms are necessarily a compromise that might perform fairly well in a broad series of applications, however excel at none of them. Using an SLR lets you select a lens, whether it’s a zoom or a repaired focal length lens (called a prime lens) that does a specific thing effectively undoubtedly. A lens with a zoom variety, extending from wide-angle to long telephoto might be plagued with distortion at one end of the variety or another (or both!). A multi-purpose lens is most likely much slower than an enhanced optic, perhaps with an f/4.5 or f/5.6 optimum aperture. With the schedule of interchangeable lenses, you can select a really quickly, f/1.4 lens when you need one, or select a lens that’s particularly excellent in a provided zoom range (say, 12-24mm). Select another lens for its splendid sharpness, or since it provides a dreamy blurred effect that’s perfect for portraiture. Use zooms when you need them and prime lenses when they are better fit for a task.

■ Lens swaps make it simple for those with extra-special requirements to discover some glass that fits their specific requirements. Fisheye lenses, those with a point of view control shifts, macro lenses for a bug’s eye view of that prize flower, or hyper-expensive super-long telephoto optics with built-in correction for electronic camera shake are offered to anyone who can afford them. As you know, however, lenses aren’t definitely interchangeable. Lenses designed to fit on one specific supplier’s brand name of video camera probably won’t fit on another supplier’s cam (although there are exceptions), and it’s highly most likely that you’ll discover that many lenses produced by the manufacturer of your digital SLR can’t be used with present cam designs. I can’t provide a thorough lens compatibility chart here, because there are hundreds of various lenses readily available, however you might discover some of the guidelines in this section helpful. The first thing to understand is that lens compatibility isn’t even a problem unless you have older lenses that you wish to use with your current digital camera. If you have no lenses to move to your new camera body, it makes no distinction, from a lens perspective, whether you choose a Nikon, Canon, Sony, Olympus, Pentax, or another DSLR. You’ll want to purchase existing lenses produced your video camera by the vendor, or by 3rd parties such as Tokina, Sigma, or Tamron, to fit your electronic camera. One exception might be if you had a hankering for an older lens that you might acquire used at an attractive cost. In that case, you’ll have an interest in whether that older lens will fit your new camera. You likewise might be thinking about backwards compatibility if you own a lot of costly optics that you want to use with your brand-new electronic camera. That compatibility depends a lot on the style approach of the video camera vendor. It’s easier to create an entire brand-new line of lenses for a new camera system than to find out how to utilize older lenses on the current devices. Some vendors opt for bleeding-edge innovation at the expenditure of compatibility with earlier lenses. Others bend over backwards compatibility.