Digital Cameras
National Camera & Digital Imaging

Megapixels
The resolution of an image is determined by the number of pixels, or tiny dots, contained within it. The higher the number of pixels, the greater the clarity and color gradations of the image. Digital cameras are categorized by their resolution, which is measured by how many megapixels (1 million pixels) they can capture with each image. The resolution is one of the single most important factors in selecting the right camera for you.

Print size
The number of megapixels in an image will determine how large you may print an image before it begins to break down and look grainy. A general rule of thumb correlates megapixels to maximum print sizes as follows:

Storage size
As the megapixels increase, so does the images file size. If you plan on taking many high-resolution pictures in a single session, be sure to have plenty of storage media to save them all. Most high-resolution cameras, however, provide the option of adjusting the resolution downward whenever you do not require a larger image, such as when shooting photos for the web or for email.

Optical Zoom
Zoom is measured by how many times closer the image appears, so a 3x zoom will magnify the subject of your image three times. Since photographers are often further from subjects than they'd like to be, zoom is a critical function of any camera.

Optical Zoom vs. "Digital Zoom"
Optical zoom is achieved by moving the camera lens, just as one would on a 35mm camera. Using optics to zoom in allows you to take pictures that appear much closer, without loosing any of the picture quality. Today's digital cameras range from a fixed lens (no zoom) to 10x optical zoom in higher-end models. An average digital camera will have a 3x optical zoom.

Digital zoom, on the other hand, is simply an electronic manipulation of the image by the camera's processor. The major drawback to this method is the appearance of tiny dots throughout the image that makes it appear fuzzy.

Generally speaking, digital zoom features are little more than a marketing ploy and should be disregarded when making a decision in purchasing a digital camera.

35mm Equivalent
Digital camera specifications usually list the 35mm equivalents for digital camera lenses. This may be helpful in determining which camera has a lens that approximates the focal lengths you are used to.

The ability to preview what the camera sees before you take a shot can be essential for capturing the best possible images. For obvious reeasons, the larger the LCD viewfinder screen, the larger the preview image you will have to work with. But, keep in mind that the LCD screen is one of the primary drains on power, so a larger LCD means a higher power usage and more frequent battery changes.

There are two ways of uploading your images from your camera to your PC. All digital cameras come with some method of direct connection that usually involves a serial or USB cable. The alternative is to connect a media card reader, which allows you to take the media out of the camera and plug it into the reader, which then uploads the images to your PC.

Direct Connect- Serial vs. USB
Serial and USB are the two most common connections for digital cameras to a PC. The differences between the two are speed and ease of swapping. USB connections will greatly reduce the amount time it takes to upload images from your camera and can be swapped out while the computer is running. Serial connections require that you shut down and reboot your PC for it to be recognized. Also, serial connections are very slow.

Reader
Card readers offer the convenience of reading images directly off the card, without having the camera attached. This allows you to conserve the batteries of the camera during uploads, and, if you use multiple media cards, you can upload images off one card while shooting images on the other.

Most cameras will come with some minimal amount of internal memory and/or a very small memory card. However, the amount of images you can store with this memory will usually be quite limited, which means that you will need larger external memory cards to be able to take several pictures between uploads. There are four primary types of external media.

Compact Flash, SmartMedia, Multimedia and MemoryStick
There really isn't any advantage between these formats, and the picture quality should be the same regardless of format. Older cameras that use SmartMedia cards may not accept some of the newer high capacity cards, so if you are upgrading an existing digital camera, you may want to see if it can read a larger card.

Size
The size of the media card, which is measured in megabytes (MB), will determine how many images will fit on it before it is full. Once it is full, you cannot take any more images until you delete some (which is usually done after you upload images you wish to keep).

Since a larger card means you can store more images, you should purchase the largest card available if you can afford. The different media formats currently have vastly different maximum capacities. Compact Flash supports a capacity of 1GB (1,000 MB), Multimedia reaches 256 MB while MemoryStick and SmartMedia max out at 128 MB.

The size of the images you take will determine the minimums you will be comfortable with. If, you plan on only taking low resolution images for the web or emails, a 16 MB card may be adequate. If you are using a high resolution camera, however, you may need a 256 MB card (or higher) for sufficient storage.

Digital cameras have three power options. Some cameras come with a proprietary rechargeable battery. Others use AA batteries, which can either be standard single-use alkaline or rechargeable NiMH batteries. Since digital cameras use up batteries so quickly, it makes economic sense to use rechargeable batteries.

Proprietary and NiMH batteries
There are advantages to cameras that use proprietary and those that use AA size batteries as well. Proprietary batteries can often be recharged in the camera itself, which is very convenient. However, the downside is that, since it uses a unique battery, you cannot run out to the corner store and grab a pair of batteries off the shelf in the event you want to use your camera when your proprietary battery is run down.

Extra pack and charger
Regardless of the type of battery the camera uses, you will probably want to invest in a spare set of batteries with a charger. Since they can drain batteries quickly, if you don't have a spare set charged and ready to go, you will likely face frustrating situations where you miss out on using your camera because the batteries are dead. If the camera has a battery charger built in, you will still want the separate charger, so one set can recharge while you shoot.