Digital Cameras

First Published: December 2002
Last Update: December 2002
Author: Sorin Chiorean, Computer Partners

This article is intended as a digital camera buyer's guide and will discuss features and functions that should be considered before making your first purchase. Digital cameras are very much like the standard 35mm film cameras that most of us are familiar with. Both contain a lens, an aperture, and a shutter.

The big difference between traditional film cameras and digital cameras is how they capture the image. Instead of film, digital cameras use a solid-state device called an image sensor, usually a charge-couple device (CCD). On the surface of each of these fingernail-sized silicon chips is a grid containing hundreds of thousands, or millions of photosensitive diodes called pixels. Each photosensitive diode captures a single pixel in the photograph to be. When the shutter opens, each pixel on the image sensor records the brightness of the light that falls on it. When the shutter closes to end the exposure, the charge from each pixel is measured and converted into a digital number. The series of numbers can then be used to reconstruct the image by setting the colour and brightness of matching pixels. Each time you take a picture, millions of calculations have to be made in just a fraction of a second. It's these calculations that make it possible for the camera to preview, capture, compress, filter, store, transfer, and display the image.

With traditional cameras, the film is used both to record and store the image. With digital cameras, separate devices perform these two functions. The image is captured by the image sensor, and then stored in the camera on a storage device of some kind (discussed later in this article).

With a digital camera you can immediately see your images on a small LCD screen on the back of most cameras. Digital photography is instant photography without the cost of film!

Once captured, digital photographs are in a format that makes them  easy to distribute and use. For example, you can insert digital photographs into word processing documents, send them to friends by e-mail, or post them on a Web site where anyone in the world can see them.

Digital cameras are becoming more than just cameras. Some of them are capable of capturing not only still photographs, but also sound and even short video clips -- they are becoming more like multimedia recorders than cameras.

Some important features of the digital cameras

If you are thinking about buying a digital camera you need to understand the following features. These are the most common features for all makes and models.

Resolution

The resolution is how many pixels the camera's image sensor uses to split-up and reassemble the picture. The megapixel rating would give you a good indication of the quality of the camera (the higher the megapixel number, the better the resolution). A 1-megapixel camera makes prints as large as 4 x 6 inches, a 1.3- to 1.5-megapixel camera makes 5 x 7-inch prints, and so on. The chart below gives you a rough idea of how many megapixels you'll need for a given print size: 

The most expensive professional digital cameras give you about 6-million pixels. Although this number is impressive, it still doesn't come close to matching the approximately 20 million pixels in traditional 35 mm film and 120 million your eye is capable of perceiving. So digital camera picture quality has a ways to go before it equals the quality of standard 35 mm film. However for web site display and normal brochure or catalogue display digital picture quality is entirely adequate.

The Camera Lens: Fixed, Optical Zoom & Digital Zoom.

To take good pictures, a camera has to have quality optics (glass, no plastic). The most common error beginning photographers make when taking pictures is to stand too far away from their subjects. Like inexpensive film cameras, many low-priced digital cameras use fixed-focal-length lenses. The only way you can change the framing of your picture with a fixed-focal-length lens is to back away or move closer.

An optical zoom lens allows you to adjust the apparent distance between you and your subject without moving backwards or forwards. You can change the framing of your picture (i.e. adjust the distance between you and your subject) by "zooming" in and out from a wide-angle to a telephoto view, or anywhere in between and the subjects will appear much closer than they really are.

Optical zoom lenses are commonly referred to by their zoom ratio, which is the difference between their focal length at the widest-angle setting and maximum telephoto. A zoom ratio of 1:3, or 3x, means that the maximum zoom range is three times further than the closest wide-angle setting. The most common zoom ratio for digital cameras is 3x, but some compact cameras have only a 2x zoom.

Don't be fooled by the terms "digital zoom" or "digital telephoto"! A digital zoom is not a true zoom lens. They work by cropping the image, throwing away the information around the edges, which increases the apparent magnification of the lens. The result, however, is decreased resolution and soft-looking images.

Image Storage

Most digital cameras store captured images on removable memory cards of one sort or another. The top three contenders SmartMedia, CompactFlash and Memory Sticks. They are available in capacities ranging from 8MB to 128MB (and some larger). This makes upgrading  your digital camera is as easy as plugging in a larger memory card! You can also use multiple cards. Just swap out the full one and pop in the a new one when the first one fills up. Be aware that some inexpensive digital cameras have only internal memory that is built into the camera, rather than on a removable card.

Computer Connection

An often-overlooked feature is data transfer: How do you get images from your camera to your computer without using a card reader? The answer is the same as with any other computer peripheral (printers, scanners, or storage drives). Most of the newer digital cameras provide a choice of two or more ways to interface to your computer. So regardless of the make, model or age of your computer you will normally be able to transfer the pictures directly from the camera to your hard drive.

The real question is: which connector works best? That's easy! By far, the fastest computer connector is Firewire (also known as IEEE 1394), but it's expensive. It is rarely found on anything but the most expensive professional models of digital cameras. Next in line, in terms of speed, is USB (Universal Serial Bus). This is the computer industry's most successful attempt to date of standardizing computer-to-peripheral connectors. 

Old computer that do not have USB ports will have to use the standard RS-232 serial port connectors. This is the slowest method of transferring image data from camera to computer, but this interface is still common on many digital cameras. Just check before buying that the interfaces on the camera match one of the interfaces on your computer..

Batteries

The camera's power source is important. Many digital cameras use standard AA-sized batteries for power, but it's important to note that cameras really don't do well on standard alkaline cells. Digital cameras draw large amounts of current, far more than alkaline batteries are designed to provide. The result can be very short battery life, sometimes measured in minutes. In fact, most digital camera manufacturers recommend higher capacity and more economical rechargeable nickel-metal hydride (NiMH) or lithium-ion (Li-ion) batteries. Sometime these are standard rechargeable AA cell, but some manufactures provide custom designed battery packs. Using custom battery packs saves on battery size and weight making cameras more compact, but buying a second custom battery as a backup can be quite expensive.

Creative controls

It's important to realize that even the most sophisticated digital cameras offer a "full auto" mode, in which the camera makes all of the exposure decisions, and the photographer just pushes the shutter button. If you leave the camera in its auto capture mode, you'll never have to deal with the complex list of features, modes, and functions that many cameras offer as shooting options. All you really need to do is snap the shutter in auto mode, view the pictures in playback mode, and transfer the pictures to your computer. However, to really be in control of your images, you have to cross the bridge into manual control. It's only then that you can creatively choose to have backgrounds out of  focus or choose between blurring and or freezing a fast moving subject Full manual creative control is generally only available on the more expensive high-end digital cameras.

Conclusion

Digital cameras have improved so much over the past few years, That even the low-end 2-megapixel models can deliver acceptable colour and quality. Our advice is to set your budget, choose the feature set you want, and then review  at all the models that fit within your budget and specifications. There are so many digital cameras with so many different features that it's hard to compare them unless you know what features are available and how they affect your photography. Lens quality is hard to quantify, as is the quality of the software inside the camera. To make the best camera choice, read reviews from sources you trust and try to look at side-by-side comparisons of images.

About the Author

Sorin Chiorean is a technical support specialist at Computer Partners.  He is well-aware of  ever-changing, cutting-edge technologies and enjoys telling everyone about them!  He has so many "techie" goodies to impart that he just may get his own "Tech Corner" on the InfoPool... so stay tuned! 

Here is some more interesting information about digital cameras:

• Digital Camera Basics
• All About Digital Cameras  
• Digital Camera HQ - reviews, prices and advice on the best digital camera models. 
• Qa Camera -- The resource for cameras!
  

Here are some interesting books about digital cameras:

• How to Do Everything with Your Digital Camera by Dave Johnson
• The Confused Photographer's Guide to Photographic Exposure and the Simplified Zone System by Bahman Farzad (Photographer), Linda Voychehovski (Editor)
• Digital Photography Click-by-Click by Jerry Glenwright