Deciphering a Data Sheet

When you shop for a dSLR, you'll find a bewildering array of options. Salespeople will hand you data sheets that describe in sometimes painful detail what the camera can do. In this section, I explain the major areas to look for when you go shopping for that first dSLR. By the way, this book's Glossary is another source of information for unfamiliar terms.

Recording Medium

The recording medium is the type of memory card used by the camera, such as CF (Compact Flash) memory cards. The most common card is Type I (3.3mm thick), whereas some, such as the MicroDrive, are Type II (5mm thick). Devices equipped with Type II slots can also accept Type I cards, but not vice-versa. Other common types of memory cards used in dSLRs are SD (Secure Digital) and xD Picture Cards (see "Memory Cards" sidebar earlier in this chapter).

Aspect Ratio

The 3:2 aspect (width to height) ratio is the most common for digital photographs and is the same ratio that a traditional 35mm film camera uses. Other available ratios you'll find are 4:3 and 16:9.

Color Filter System

Most dSLR image sensors use an RGB filter to record a single color on each photosensor to produce an accurate image. The exception is the Foveon X3 sensor which uses a color-separation beam-splitter prism assembly and utilizes all the light and records all colors at all locations on the sensor. This technology is currently featured in the Sigma line of dSLR cameras.

Recording and Image Format

A dSLR should take and store photos in both JPEG and raw formats. This means that images are written to the memory card in a way that can be understood by image-editing programs. Although JPEG is a widely accepted format in virtually every software application, raw files are proprietary to each individual manufacturer and require their software, or a licensed third-party application, to convert to an editable file.

File Size

Most cameras support saving JPEG files in various sizes up to a limit, normally given as maximum file size. This is the recommended manner for capture to ensure the best quality enlargements. Shooting smaller files is quicker, allows more images to be stored on a card, and is ideal for Web use.

Image-processing Parameters

Some cameras enable you to create preset custom settings that can be quickly recalled for shooting specific situations, eliminating the need to select each individual setting from the menus every time you want to use them.

Interface

The interface is how the camera is connected to your computer. You'll find either USB 2.0 or FireWire (IEEE 1394) as options. Be sure your computer has a FireWire port if you choose a camera with a FireWire interface.

White Balance

With most dSLRs, the white balance, measured in degrees Kelvin, can be set for the appropriate light source. Presets for daylight, shade, cloudy, tungsten, fluorescent, and flash are common options. All digital cameras also provide an Auto preset where the camera can more accurately determine the proper white balance based on the current light source. Finally, most cameras also let you create a custom setting for a mixed light source or specific lighting situation, such as in a studio.

Viewfinder Coverage

Most viewfinders don't show you the entire image being captured. More expensive pro-level dSLRs often have 100-percent viewfinder coverage. This is a tremendous advantage for properly evaluating composition and framing.

Magnification

The magnification level in the viewfinder relates to how large the scene appears when you look through the eyepiece. A magnification of .8x is considered very good.

Viewfinder Information

This is a listing of all the information that can be displayed in the viewfinder around the frame. Thankfully, you'll never see all of it at once. Chapter 4 has more details on reading the information in your viewfinder.

Depth-of-field Preview

Landscape and macro photographers in particular find a depth-of-field preview very helpful. This works by closing the aperture down to the selected setting to let you see what areas of your scene are in focus before you take the shot.

Eyepiece Shutter

For long exposures, it's helpful to cover the eyepiece to keep stray light from entering. Some pro cameras have a built-in shutter, and others come with a simple cover you can snap on.

ISO Speed Range

The speed range refers to the different range of ISO (International Organization for Standardization) film speed settings you can use. Many dSLR cameras can go as high as ISO 3200. Remember though, just as in 35mm photography, the higher the ISO setting, the more noise (graininess) issues you'll have with the image. You can use higher ISO settings in lower light situations to increase the sensitivity of the sensor just as you would by using faster film with a traditional camera. I cover ISO in more detail in Chapter 2.

Exposure Compensation

Exposure compensation, in the form of f-stops, adjusts the camera to automatically add or subtract some light from the exposure setting you're using. This is useful when shooting very bright, backlit subjects or very dark scenes. Essentially, it instructs the camera to overexpose or underexpose an image based on what the camera would incorrectly perceive as the correct exposure setting. Bracketing is a feature that enables the camera to take a set of images, usually three, with different settings to increase the chances of capturing one correctly exposed image.

Noise Reduction for Long Exposure

Built-in noise reduction works by taking a second image without opening the shutter. This is called the dark. The camera then compares the dark and the real image, and wherever there are matching pixels, or noise, they are removed and replaced with dark pixels.