WASHINGTON, 16 September 2003 — Digital cameras may seem miraculous, but like most things digital, they’re built upon a logical foundation of zeros and ones. Indeed, while it’s easy to throw around terms such as “pixels” and “megapixels,” those who understand what those terms mean and how they’re used by digital cameras will be in a better position to distinguish higher quality models from those that you should pass by.
— The basics
Tell someone you have a digital camera, and if they’ve been looking into the technology at all, they’ll probably ask you how many megapixels it has. It’s as though the amount of megapixels provides a direct correlation to the quality of the camera. It doesn’t. The camera manufacturers are partly to blame for this misunderstanding, as they have taken to distinguishing their models by touting the number of megapixels they sport.
But just what is a megapixel? The word “ megapixel” stands for “one million pixels.” The word “pixel” is a shortened form of “picture element,” the building block of all digital photographs.
In essence, a digital photograph, while it looks smooth and continuous like a photo taken from a film camera, is made up of millions of tiny picture elements, or pixels. If you open a digital photograph in an image editor, such as PhotoShop, and enlarge it to 1,000 times its intended size, you’ll easily see each of the tiny squares, or pixels, that form the digital photograph when viewed from a distance.
Each pixel in a digital photograph has a numerical value which determines its shade. The shade is composed of a combination of three colors: Red, blue, and green. Hence, if you run across the term RBG in your photograph editing, you know that you’re dealing with a basic color scheme used by digital cameras as well as other digital imaging devices.
— What the numbers mean
Of course, one pixel alone does not a picture make. Indeed, today’s digital cameras take pictures composed of millions of pixels, or megapixels. Manufacturers use the number of megapixels that each camera can capture as a way to distinguish their products from those of other manufacturers. The implication is that the more megapixels the camera supports, the better the photographs.
This is only partly true. While in general cameras that cram more pixels into their photos will provide sharper output, the size of the imaging sensor — the camera’s main light-gathering chip — also plays a role. Most digital cameras on the market today contain tiny, fingernail-sized sensors, generally about 7mm x 5mm, and the pixels on the sensors are very small.
Larger sensors are usually supplied with more expensive digital cameras. These sensors, while they may sport the same number of pixels as those found in cheaper digital cameras, have room for larger pixels, which can record more information about the subtleties of light hitting the sensor. The more subtle the information that is conveyed from the sensor to a camera’s electronics, the more realistic is the resulting photograph.
In short, there’s a lot more to digital picture quality than the number of pixels present in a given camera. With more expensive cameras, you’re generally buying a more sophisticated light-gathering instrument.
— Gizmos and gadgets
If your goal is to purchase a digital camera that takes pictures equal to or better than a film camera, you’ll want to avoid cameras with some common features found in lower end units.
Many people, for example, like the “live preview” that some digital cameras offer, allowing you to bypass the viewfinder and see your picture composed on the rear LCD. Cameras that offer this feature, however, use a type of sensor technology known as “interline transfer,” which allows for data to be read from the sensor in real-time and displayed on the back of your digital camera.
In order to get this live display, interline transfer sensors must devote part of each pixel area to non-light-gathering activities — namely storing picture information so that you can see it on your back screen. This means less light information is available for the actual image stored on your film card. It’s these type of cameras, too, that allow you to take short videos as well as still photographs.
You’ll notice that more expensive digital cameras, those that resemble film cameras in appearance and operation, eschew the live preview option, since they use the entire sensor space for capturing light information.
The bottom line is that if you want a high-quality digital camera, you need to be looking at more than how many megapixels it supports. Today’s digital cameras are rated at anywhere from 1 to 14 megapixels. But some cameras rated at just 3 megapixels, such as the Canon D30, now widely available on the used market, take superior pictures to cameras rated at 5 or 6 megapixels.
