Megapixel Digital Concepts

Generally speaking, a camera with more megapixels will produce greater quality images.

When Kodak Eastman Engineer Steve Sasson filed a patent for the first digital camera in 1975, his device took a .01-megapixel image. Since the launch of Dycam's Model 1 (1990), digital technology has become the standard for photography and imaging in many fields, with today's commercial cameras offering images of 15 or greater megapixels. The number of megapixels accounts for the potential size of a digital print, but does not always indicate its potential quality.

Pixilation

The pixel is the fundamental unit of a digitally produced or recorded image. Each pixel consists of information about its location, or "photosite" address in the image, and the pixel's color and intensity, all of which it stores as a series of numbers. The term "megapixel" denotes 1 million pixels, set in an array. The size and dimensions (length vs. height) of this array depend on the camera and its sensors. Generally speaking, a camera with more pixels can store more information, and produce images with greater detail.

Megapixel

A digital camera uses one of two types of sensors to construct its megapixel array, either a CCD or CMOS image sensor. Both of them function in the same manner, building the overall array from a rectangular grid of single sensor elements. Each single sensor element records 1 pixel of information. The megapixel rating of a camera denotes the number of single sensor elements present in this rectangular array. For instance, a camera whose CMOS sensor consisted of a length of 3,072 single senor elements and a height of 2,048 single sensor elements would have a megapixel rating of 6.3 (3,072 x 2,048 = 6,291,456, or 6.3 million pixels). Commercially available cameras such as the Canon EOS Rebel and the Fujifilm Finepix A610 possess this 6.3-megapixel rating.

Sensor Size

Even in cameras with the same megapixel rating, the size of the sensor (CCD or CMOS) affects the quality of the image. A bigger sensor will contain larger pixels, giving the resulting image greater clarity, more detail and better overall quality. Generally speaking, the more compact a camera, the smaller size sensor it uses. The larger body of an SLR (single lens reflex) or a professional camera can house a much larger sensor.

Megapixels vs. Print Size

The number of megapixels that an image contains will directly affect the quality and maximum print size of the resulting image. Printers use a "dots per inch" (dpi) setting to determine the quality of a printed image or document.

The number of "pixels per inch" (ppi) in an image shot by a digital camera loosely corresponds to dpi. A camera's megapixel rating and sensor size determine the ppi; cameras with higher megapixels will yield greater ppi. As the size of a print increases, it must spread the existing ppi of the image across a larger dpi area. The more megapixels a camera can produce, the higher the ppi and the greater the resolution and quality of the resulting photo, especially as the print size increases.

References

• Cambridge in Colour: Basics of Digital Camera Pixels
• Scanning Tips: What is a digital image anyway?
• Digicam Help: What is a megapixel?
• Practical Photography Tips: History of Digital Photography
• Ken Rockwell: The Megapixel Myth
• Digibarn Computer Museum: Dycam Model 1 The world's first consumer digital still camera

Resources

• Digital Photography School: Directory