Almost Everything You Ever Wanted To Know About Digital Cameras

PSA Journal, August, 2000 by Richard M. Frieders

Digital cameras have been available for only a few years and in that time we have seen the quality of the image increase so that it now compares to one taken with a regular film camera. These new electronic cameras can be connected directly to a computer so you can view the images, enhance them or make corrections, print them, save them or put them on a web page.

Digital cameras could be grouped into three categories -- Entry level, intermediate and professional. The entry level would be those that are priced below $500. Intermediate would be between $500 and $1000 and the professional versions would go up from there.

New features continue to appear and prices continue to drop and, like computers, new versions hit the market every few months. There are now several new full-featured SLRs available for less than $5000. These are Nikon D1, the Fuji S1 and the new Canon D30. Cameras in this category were more than twice that price a few years ago.

* Camera Specs

Digital cameras vary greatly and some of the terms used when describing the camera are quite different than what we're used to with our film cameras. Other terms are the same, but may mean slightly different things and some terms are completely new.

* Resolution

Probably the most important specification to consider is the "resolution" of a camera. This indicates the amount of detail the camera will be able to capture. Resolution is expressed in numbers of pixels, or picture elements, such as 640 x 480 = 307,200 or 2160 x 1440 = 3,110,000 (3.1 megapixels). These numbers actually indicate the numbers of pixels horizontally and vertically on the sensor in the camera. The higher the number of pixels, the higher the resolution and the better the quality of the image. This image sensor, or "CCD" for Charge Coupled Device, takes the place of the film in a regular camera. It captures the light when the image is taken and translates the light levels into digital signals that the camera can then process. Low resolution cameras are fine if you plan to print small prints or use the images for web use. If you want to be able to print large prints, then you'll want a camera with as higher resolution. At this point in time, the higher resolution cameras are in the 3 to 4 megapixel range.

All digital cameras capture images in full color, but if you prefer a black & white image, you can convert it very easily with your computer. All images are made of pixels and each pixel is a different color. Most cameras will generate an image using 256 shades of red, 256 shades of blue & 256 shades of green. This combination of numbers means that it's possible for each pixel to generate any one of 16.7 million colors.

* Speed

Unlike film cameras where you can use different speed film, most digital cameras are set for a film speed equivalent of ISO 100. Many new ones come with additional speeds such as 100, 200 & 400.

* Lens

Many of the lower priced cameras come with a fixed focal length lens, other have zoom lenses and a few in the higher priced category have interchangeable lenses. Some of the zoom lenses offer both optical zoom and digital zoom. The optical zoom is the best as elements in the lens move to change from wide angle to telephoto, whereas a camera with a digital zoom does so electronically and you may tend to see the pixels in the image. The focal length of a lens for a digital camera depends on the size of the CCD sensor. Most camera manufacturers use a lens that will give you the same area of view that you would see with a standard 50mm lens on your 35mm camera. Auto-focus is found on most digital cameras although some do allow manual focusing.

* Memory Cards

These small devices, measuring a little over an inch square and an eighth of an inch thick, plug into the camera and are used to store the images that you take. There are several types of memory cards and each type has different memory capacities available. This memory ranges from 4 Mb to several hundred Mb and the amount will determine how many images you can store on it. The most popular ones are known as "Smart Media" and "Compact Flash." As the camera takes the images, they are transferred to the card until it is "Full." The images can then be transferred directly to the computer by way of a cable or the card can be removed and put into a "reader" for transfer. The card can then be used over and over again to store more images. There are many other devices to transfer the card's contents and save them. You can also insert the card into a small viewer to look at the images, or into printers to print the images.

* File Format

Most cameras offer you a choice as to the format of images you would like to take. If you want the highest quality possible, perhaps for printing a fairly large print, you would use a regular "TIF" format. If you are working with smaller size prints or with images to put on a web page you have the option of "compressing" the images. The camera will electronically save the image in a lower resolution or "JPG" format. This means a memory card may save 50 low-resolution images but only 10 high resolution ones.