The SLR cameras and lenses certainly attract a lot of interest and they do offer advantages over cameras with built-in lenses. If you're thinking about upgrading from a compact digital camera, consider the pros and cons of a D-SLR as well as the prosumer models with a built-in lens. Photos © 2003, Peter K. Burian, All Rights Reserved

Through The Lens (TTL) Viewing
The term Single Lens Reflex refers to the fact that you view the scene through the same lens as you will take the picture. In an SLR camera, through the lens viewing is provided by a mechanical system. A "reflex" mirror reflects the image to a prism, a device with a system of mirrors that reflect the image to the optical viewfinder. Consequently, there is no need for a secondary viewing lens of the type found in most cameras with built-in lenses. Because you view the subject through the "taking" lens, framing is highly accurate.

With most compact cameras you view through a small secondary lens or viewfinder above the "taking" lens. That's fine for most situations, but in very tight close-up or "macro" shots--with the subject less than about 24"from the camera--the framing will be inaccurate. Because the two lenses "see" slightly different parts of an image, you may cut off the top of your subject in the pictures. Naturally, you can use the LCD monitor to frame the subject; this is useful in extreme close-ups but increases the risk of blur from camera shake when holding the camera away from your body. It might also not be so easy to see accurately when shooting in bright sunlight.

A camera that allows you to view the subject through the "taking" lens offers highly accurate framing, a benefit particularly in close-up photography.

Cameras with 5x and longer built-in lenses also offer through the lens viewing but they use entirely different technology: a small LCD screen (like the type used in video camcorders) inside the viewfinder. Because the electronic viewfinder (EVF) allows you to view the subject through the "taking" lens, some publications refer to such cameras as single lens reflex models. This is not correct, because they do not employ the reflex mirror and prism mentioned. When using the term SLR, I'll refer only to true Single Lens Reflex cameras that also accept a wide range of interchangeable lenses.

Compact Cameras Pros And Cons
Before moving on to consider the merits of D-SLR cameras, let's take a look at the benefits and disadvantages of digital cameras with a built-in lens, still the most popular type.

PROS
· There are far more such cameras on the market. This wealth of choices gives you much greater flexibility in selecting just the right model, with the size, appearance, price, capabilities, resolution (megapixels), and features you desire.
· While the high-end "prosumer" cameras are packed with a multitude of SLR-style capabilities, you can find many others that are quite easy to use. Such cameras often include all of the essential features and they're primarily designed for simplicity and convenience of operation.
· The cameras with built-in zoom are more portable than a D-SLR with lens attached, and offer greater convenience. Some--including a few of the 5-Mp models--are particularly compact; you'll be more likely to carry (and use) a camera of this type so you won't miss any photo opportunities.
· Some of the mid to higher priced cameras accept optional telephoto and wide angle adapters, filters and high-powered flash units; these allow you to expand their versatility.

While a prosumer camera with a high-resolution sensor and wide range zoom lens can be useful for some serious photography, a D-SLR system offers advantages when you need an ultra-wide angle or super telephoto lens..

CONS
While these advantages are certainly meaningful, cameras with a built-in lens are not ideal in all respects. Consider the following issues:
· Except for the prosumer models, cameras with a built-in lens offer fewer advanced capabilities for serious photography than the D-SLR cameras.
· All cameras with a built-in lens employ smaller sensors than D-SLR cameras, with smaller pixels. Consequently, they do not produce the same level of image quality, particularly at high ISO settings and in most low-light photography.
· A built-in zoom lens--even with an extra-cost adapter--is not nearly as versatile as an SLR system with a wide range of lenses.
· In extreme close-up photography, cameras with an optical viewfinder do not produce accurate framing. You must use the LCD monitor to compose your images in such situations; this increases battery consumption and the risk of blurry images from hand and body tremors when holding the camera away from your body.
· Cameras with an electronic viewfinder (discussed in our TTL sidebar) provide accurate framing, but the view through an EVF is not as bright and crisp as through an optical viewfinder. As well, there's a delay from one shot to the next while the EVF refreshes to provide a live view of the subject; that can make continuous framing of a moving subject difficult.

Digital SLR Pros And Cons
In addition to the benefits of an optical through the lens viewfinder, a D-SLR camera has several advantages over the models with built-in lenses:

A camera with a built-in 28-200mm or 35-280mm zoom is smaller and lighter than a D-SLR with a short lens. If you decide to buy an SLR--especially with extra lenses and accessories--you'll want a compact camera as well for situations where you need more portable equipment..

PROS
· As a general rule, they're quicker to start up, allowing you to take the first shot almost instantly. There's virtually no "shutter lag": the delay between pressing the button and the instant of exposure; this allows for capturing a fleeting smile, gesture, or a moment of interaction.
· Their autofocus systems are generally faster and D-SLRs also offer faster framing rate and greater burst depth (for more images in a sequence); granted, the best of the prosumer cameras come close in these performance aspects. If you like sports or action photography this will be a big plus in D-SLR's favor.
· The manual focus system is far more effective and more convenient to use.
· You can determine exactly what is in focus at a glance because the exact area of sharp focus is clearly visible in the viewfinder. That's not possible with compact cameras with an optical viewfinder and it's difficult to see with a (tiny) electronic viewfinder.
· The 6-megapixel D-SLR cameras generate cleaner images than the 8-Mp cameras with built-in lens; the images can be enlarged to a much greater extent without an appreciable loss of quality, great for making 13x19" prints. If you often shoot in low light, you'll find that the D-SLR images exhibit less digital noise (random colored specks) in long exposures or at high ISO settings.
· A D-SLR system offers unparalleled versatility because it includes numerous lens types. These range from ultra wides that encompass more than our own eyes, to the super telephotos necessary for making tightly framed images of sports, racing, and wildlife subjects. No matter what type of photography you enjoy, there is a lens that will help to achieve your exact intentions.
· D-SLR cameras offer extra features not available even with the most expensive prosumer cameras. My own favorites include: depth of field preview (to assess the range of apparent sharpness, behind the subject and in front of it); and reflex mirror lock up to minimize internal vibrations in high magnification macro photography; and a more reliable autofocus system with true tracking focus for action photography. (Most prosumer cameras with built-in lens include continuous autofocus but this is less reliable with fast moving subjects.)

An increasing number of prosumer cameras include continuous autofocus option useful for slow moving subjects; a few Minolta models even include a tracking focus option for following subjects moving at a faster rate. However, an SLR camera's tracking focus mode is more reliable with high-speed action especially with erratic motion such as acceleration. (Sigma SD9 SLR with 70-200mm zoom.)

CONS
Before you start saving up for a D-SLR camera, consider the drawbacks too:

· The extra size/weight means less portability so the camera may be left behind more often.
· The camera will be more complicated to operate than most of the cameras
with built-in lens, except for the
prosumer models that are also packed with capabilities.
· All of the consumer grade D-SLRs employ an image sensor that's smaller than a 35mm film frame (the industry standard); hence, the cameras produce a "focal length magnification" factor. That's great if you love telephoto photography because a 200mm lens provides the equivalent of a larger/heavier 300mm (or 320mm) lens on a 35mm camera. But for true ultra-wide angle photography you'll need to buy a very short lens such as a 12-24mm or 15-30mm zoom.

The Bottom Line
In most respects, cameras with built-in lenses offer greater value and some of the prosumer models are incredibly useful for most types of serious photography. Nonetheless, a D-SLR camera system is even more versatile, more reliable in some respects, and is capable of producing higher image quality. Of course, much of this benefit depends on your own needs and budget. Do you intend to buy a series of lenses and a printer that can handle up to 13x19 prints? And do you often shoot sports or low-light scenes? If not, you should be happy with a top rated camera with a built-in lens, particularly a 28-200mm (equivalent) or similar zoom.

But if you're serious about digital photography and imaging--or if you plan to develop in that direction--a D-SLR camera will keep your options wide open. Start with a modest zoom and an affordable photo printer and expand the system as your budget and your demands increase in the future.

If you decide to buy a D-SLR, narrow the field down to a couple of models that include the capabilities that you want or are compatible with lenses that you already own. Then, visit a well-stocked retail store and ask to handle each camera. Check the type of controls, general handling, responsiveness and the logic of operation; select the one that you find most convenient to use. This "test drive" may be the single most important step, helping to assure long-term satisfaction with your new system.

A long-time eDP and Shutterbug contributor, stock photographer Peter K. Burian is the author of a new book, Mastering Digital Photography and Imaging. ($21 through online bookstores.) Covering all aspects of the topic--the technology, equipment and techniques--this book provides 270 pages of practical advice for photo enthusiasts.