Digital Imaging Explained
By Warren Lynch www.wlynch.com
Digital Imaging is a process where an electronic photograph, scanned document, or image is converted into a series of electronic dots called pixels. Pixels is an acronym for "picture elements".
After the image is converted, or digitized, it is stored on a memory storage device which may be a hard drive or some sort of electronic storage device such as a memory stick. The pixels are stored in a compressed format to save storage space.
As each pixel is being created it is assigned a color value, called a tonal value, of black, white, shades of grey, or an actual color. These pixels must be processed by a piece of software in order for them to be called up and viewed as an actual image later.
Traditional cameras capture images onto film while digital cameras use an electronic chip known as a Charged Coupling Device (CCD). The CCD is actually a grid of miniature light-sensitive diodes. These diodes convert photons (light) that strikes them into electrons (electrical impulses). The technical name for these diodes is 'photosite'. The brighter the light is that hits the photosite the stronger the electrical charge is that's produced.
After converting the photons into electrons, a mini-computer, located inside of the camera, reads the stored electrical value in each photograph. Then a built-in analog-to-digital converter turns the stored electrical value into a digital value. These digital values are then stored on the cameras memory storage device. When these digital values are recalled by software, and displayed on a screen, they reproduce the image that was originally captured by the camera or digital input device.
The digital image that is created by the CCD is huge. It's far too big to be easily stored in the relatively little amount of storage space that's available to a digital camera. Accordingly, the camera's computer compresses the image to make it smaller.
There are two basic methods for achieving this compression. The first method takes advantage of repetitive patterns in the image. For example, if you are taking a picture of an airplane that is flying in the sky, a lot of the picture will be a chunk of blue sky. The camera recognizes that there are multiple parts of the image containing the same digital information, so it only records a small piece of the sky. Then it simply creates a map to tell it where the rest of the sky belongs. When the picture is ultimately displayed the sky appears exactly the same as it did in the original image when it was first captured. The only difference is that the overall storage requirements were reduced thanks to the camera's clever mapping techniques.
The other method uses a procedure called irrelevancy. This methodology automatically removes digital information that is not visible to the human eye such an infra red light.
Digital imaging is amazing yet we have only started witnessing the revolutionary changes that are yet to come.
Warren Lynch has been shooting commercial photography since the 70's. Clients include Several Regional and National accounts. Sign up for "The Digital Dose" and receive his Digital Photography tips every other week for FREE! http://www.photopheed.com.