Camera Features

Once you've decided on the price range and image sensor type that fits your budget, it's time to look at other features. Although every camera shares some common characteristics, each company adds its own unique touch to the cameras it sells.

Every dSLR camera, regardless of cost or skill level, includes at a minimum the major shooting modes:

• Aperture Priority lets you control the aperture (and thus depth of field) while the camera selects the appropriate shutter speed.

• Shutter Priority (or Time Value) lets you set the shutter speed while the camera selects the aperture.

• Program chooses both shutter and aperture for you.

dSLR cameras also include a Manual mode in which you control both shutter speed and aperture. By utilizing the built-in meter, an accurate combination of shutter speed and aperture can be applied to capture a properly exposed image, just as in 35mm SLR film cameras.

You should also be able to choose between manual focus and auto-focus, and every dSLR I've come across lets you choose whether you want continuous auto-focus for tracking moving subjects or single auto-focus for stationary subjects.

Finally, you have a choice of metering modes. All cameras have some form of matrix metering, where the entire scene is evaluated by the camera's meter and averaged for the best exposure, and a center-weighted metering mode, where just the central portion of the image is considered for exposure. I cover metering modes in Chapter 4.

For example, some cameras have an anti-shake feature that minimizes vibration, especially at slower shutter speeds, resulting in sharper images. Canon and Nikon both offer anti-shake with some of their lenses (see Chapter 3). Pentax and Sony build the stabilization into the camera body itself, so any lens you use is stabilized.

Get ready for the wonderful world of dust. Compact cameras don't have this problem because you never remove the lens and the system remains sealed from outside elements. With a dSLR, however, every time you change lenses you expose the sensor to dust in the air. And, because a sensor is electrically charged, it acts like a magnet. You'll know that you have dust on your sensor when you see spots in your photos (Figure 1.15) that remain constant from one image to the next. In Chapter 8 you learn how to use an image-editing program to remove dust from your photos.

Figure 1.15. Dust on the sensor can be a problem for most cameras. Olympus uses a special filter to remove dust when you turn the camera on.

A couple of manufacturers incorporate dust removal into the camera itself. The Olympus E Series has a "Supersonic Wave Filter" which vibrates the sensor briefly on start-up to shake any dust off the sensor before you start your photographic session.

Lens Selection

Owners of Canon EOS and Nikon film SLR cameras will be happy to know that your existing lenses will work with the new digital body, making your purchase decision that much easier. If you're just getting into SLR photography, the types of lenses available for the camera body should be high on your list of priorities when you select a body.

Almost all dSLR cameras are sold as a kit that includes the camera body and a default lens. Most lenses chosen by the manufacturer are zoom lenses and address a wide range of situations from regular portrait or scene photography to adequate telephoto uses. These lenses are absolutely fine, but you may want to explore other options.

The type of photography you are interested in will drive your lens choice. Landscape photography fans will want to look into a system with good wide-angle lenses, while the wildlife fan is going to want a selection of telephoto lenses to get closer to elusive subjects. The nuances of these specialty lenses vary (see Chapter 3).

A final consideration with lens selection is the availability of third-party lenses such as those from Sigma, Tamron, and Tokina. These companies make lenses for Canon and Nikon as well as for Olympus, Pentax, and Sony. But you'll find the widest selection of lenses for Canon and Nikon brands.

If your interests include underwater photography, housings are available for Nikon and Canon, along with special flash units designed to be used underwater. For small, detailed subject matter, Olympus, Nikon, and Canon all offer special flash units for macro photography (Figure 1.16).

Figure 1.16. Special flash units are available from some companies. This flash, from Canon, is designed to be used for macro photography.