FILM CAMERA: Most people are familiar with the simplicity of the film camera. You put a roll of film in the camera, shoot pictures until the spool of film (cassette) is used up. Normally, 36 images is the maximum on film. You take the cassette to the photo shop and they use chemicals in a dark environment to develop the negative and make prints for you. You don’t get to see the results until the shop hands you the prints.

DIGITAL CAMERA: (see illustration) The digital camera replaces the film with a tiny electronic image sensor, which remains in the camera. The image falls on the sensor after passing through the lens. The images are transferred from the sensor to a memory card as the pictures are taken. The memory card may hold hundreds or even thousands of images.

REVIEW & ERASE: Since the images are electronic, they can be reviewed during the session on the LCD screen. An image that is not a "keeper" can be erased, allowing you to re-shoot the scene if you wish. After you transfer the images from the memory card to the computer and the images are erased from the card, you may use the card again almost indefinitely. There are many types of memory cards. The one shown above is Smart Media.

MEGAPIXELS: The image sensor is rated by the maximum number of photo-sensitive areas (pixel locations) on its surface. A camera whose largest image is 2048 x 1536 pixels is called a 3-megapixel camera (2048 x 1536 = 3,145,728). A megapixel is one million pixels. Digital cameras allow selection of smaller sizes for e-mail, etc.

HOW MANY MEGAPIXELS DO I NEED?: There are many 3-megapixel cameras available at reasonable prices. A camera of this rating can provide just about all the resolution you need for prints up to 8" x 10". Note that 4 and 5-megapixel cameras do not cost much more and they provide additional pixels if cropping is needed.

THE LENS: What is more important is the quality of the lens and special features. Optical zoom greater than 3x is very desirable. Macro-focus - the ability to focus very close to a small object is a very handy feature. Additionally, you may want video and audio capability.

ZOOM: There is an important difference between optical zoom and digital zoom. Only the lens itself is capable of true optical zoom (magnification). Digital zoom is manipulated electronically by using the middle pixels of the image on the sensor and discarding the surrounding portion. The quality of this scheme is lower than optical zoom, so it has limited use. I don’t find much use for digital zoom.

LOW-LIGHT FOCUS: I personally would not be interested in a camera that has trouble focusing in diminished light. That situation comes up often and you cannot get a good image if the camera will not focus. Look for a feature called AF (auto-focus) assist. Basically, it is a light (white or red) that temporarily illuminates the subject long enough to obtain focus.

© 2004 Fred Hall