When you upgrade from your first digital camera to a digital SLR (single lens reflex) camera, the stakes increase dramatically. Digital SLR cameras have interchangeable lenses and generally cost quite a bit more than any basic point-and-shoot digital camera. Take a look at the individual features of the dSLR (digital SLR) cameras you're considering and how they affect you.
Lenses
The ability to swap optics is the reason the word lens is so important in the abbreviation SLR. Some factors to consider when choosing a dSLR camera include:
- Lens quality: Are the lenses of a particular vendor known for their quality, both optically and mechanically (what is known as build quality)? Does this vendor offer multiple lens lines with economy lenses that may be a little less rugged but affordably priced, as well as professional-style lenses with the ultimate in sharpness and ruggedness? Depending on the type of photography you do, trading off a little weight and replacing a few metal parts with tough plastic could be important. Or, you might require lenses that can take punishment and still deliver sparkling results.
- Focal length ranges: Some vendors are stronger in the telephoto lens department and weaker when it comes to providing wide-angle lenses. Some do a better job with certain kinds of zooms than others. Make sure that the vendor of the camera you're contemplating offers lenses in the focal lengths and maximum apertures you require. If not, see if you can fill in the lenses you require from third-party vendors. It's best to see if the lenses you'll need are readily available at a price you can afford. Figure 1 shows a typical lens furnished with a digital SLR.
Figure 1: This lens is a little slow but it covers a useful focal length range.
- Special features: Focal lengths, zoom ranges, and maximum aperture aren't the only features you want in a lens. Your needs could include close focusing, fast autofocus (which depends partly on the design of the lens), or the ability to control the out-of-focus areas of an image.
Sensors and image processors
The sensor and digital signal processor has as much effect on your final image as the lens does, so be sure to check out the qualities of your dream camera's imager very carefully. In particular, look into the following:
- The amount of noise it generates at low ISO settings (ISO 100 or ISO 200) and at higher ISO settings (ISO 800 and above): Some photographers like the lower noise produced by the prosumer Canon digital cameras compared to that of competing Nikon dSLRs. Others find the Canon images so smooth they look plasticky and prefer the extra sharpness and texture of the Nikon sensor.
- The sensor's dynamic range: Is there detail in both shadows and highlights? Are colors accurate? Do the images look sharp? If you answered "no" to any of these questions, you probably need to keep looking for the right camera.
CMOS (complementary metal-oxide semiconductor) and CCD (charge-coupled device) image sensors show little difference in quality these days, but significant differences exist among sensors from different vendors. Do some comparisons now so you'll be happy with your camera later.
Exposure systems
Exposure systems range from simple spot metering to center weighted to complex evaluative systems that examine a huge matrix of points to arrive at the correct settings. Often, all three systems dwell in harmony together in one camera.
Focusing systems
The focusing system of a dSLR depends partly on two factors:
- The mechanisms built into the lens, which move the lens elements to the proper position at the camera's direction.
- The electronics in the camera that evaluate the contrast of the image to decide exactly where the correct focus point is.
You definitely want a camera with an efficient autofocus system, one that focuses accurately. You sometimes need to specify the point the camera should use as the point of focus, especially when your main subject is not in the center of the viewfinder. It's a good idea to be able to specify that the camera locks focus when you press the shutter release halfway down, or that it can continue to seek a focus point for moving subjects right until the instant of exposure.
You might appreciate a camera that can predict where the focus point will be when a moving object is racing toward or away from the camera. You also might want the ability to change quickly to manual focus by using a switch. Some kinds of photography work best when the photographer has complete control over focus.
Special features
Digital SLRs are rife with special features such as image stabilization, time-lapse photography, and so forth. If you have specialized needs, then your requirements will be specific. For instance, if you like to photograph the progress of blossoming flowers or construction, you might require the ability to connect to a computer. If infrared photography is your most important application, you need a camera that's especially sensitive to infrared illumination. If you do have special needs, pay particular attention to how well your potential new digital camera fills them.
