NORDview: Digital Camera Imaging

Digital Camera Imaging

Digital Camera Components

A typical digital camera has the following major components:

The function of each component is as follows:

Photo File Size

The most noticeable variable among digital cameras is the light sensor. The light sensor used in most cameras is a semi-conductor chip called a CCD (charge-coupled device) that captures the image in a rectangular array of pixels (photo elements). The brighter the light entering a pixel of the CCD, the larger the digital values recorded for that pixel.

The number of light sensors in a camera determines its basic image resolution.

To fill a 600x800 pixel computer screen requires an array of 600 light sensors vertically by 800 light sensors horizontally.

Since light sensors respond only to light intensity, not color, a set of light sensors is required for each of the 3 primary colors: red, green and blue.

Since many light sensor discern 256 brightness levels, 1 memory byte (1 byte can represent 256 different values) is required for each light sensor.

Resolution is more critical when the image is printed. If the 600 x 800 pixel photo described previously is printed by a 300 dot per inch (dpi) desktop color printer, the resulting print is,

If this photo is printed in a 1200 dpi magazine, the published print is too small to even be recognized.

To produce a standard 3.5x5 snapshot print using a 300 dpi printer requires a 1050x1500 pixel image producing a 4.725 megabyte (MB) file. An 8x10 print requires a 2400x3000 pixel image producing a 21.6MB file.

Digital cameras use data compression (e.g., JPEG) to reduce the photos memory requirements but at the expense of image quality. A 2:1 compression may still produces a good quality image and is often described as a high-resolution image. An 8:1 compression seriously degrades image quality and is often described as a low-resolution image. Returning to the 4.725MB file that produced a 3.5x5 snapshot print, a camera with a 8 megabyte digital film (i.e., flash memory card) storage could therefore store either

or combinations thereof.

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