Digital Imaging Explained
By Warren Lynch, Fri Dec 9th

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 ofelectronic dots called pixels. Pixels is an acronym for "pictureelements".

After the image is converted, or digitized, it is stored on amemory storage device which may be a hard drive or some sort ofelectronic storage device such as a memory stick. The pixels arestored 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 anactual color. These pixels must be processed by a piece ofsoftware in order for them to be called up and viewed as anactual image later.

Traditional capture images onto film while digitalcameras use an electronic chip known as a Charged CouplingDevice (CCD). The CCD is actually a grid of miniaturelight-sensitive diodes. These diodes convert photons (light)that strikes them into electrons (electrical impulses). Thetechnical name for these diodes is 'photosite'. The brighter thelight is that hits the photosite the stronger the electricalcharge is that's produced.

After converting the photons into electrons, a mini-computer,located inside of the camera, reads the stored electrical valuein each photograph. Then a built-in analog-to-digital converterturns the stored electrical value into a digital value. Thesedigital values are then stored on the memory storagedevice. When these digital values are recalled by software, anddisplayed

on a screen, they reproduce the image that wasoriginally captured by the camera or digital input device.

The digital image that is created by the CCD is huge. It's fartoo big to be easily stored in the relatively little amount ofstorage 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. Thefirst method takes advantage of repetitive patterns in theimage. For example, if you are taking a picture of an airplanethat is flying in the sky, a lot of the picture will be a chunkof blue sky. The camera recognizes that there are multiple partsof the image containing the same digital information, so it onlyrecords a small piece of the sky. Then it simply creates a mapto tell it where the rest of the sky belongs. When the pictureis ultimately displayed the sky appears exactly the same as itdid in the original image when it was first captured. The onlydifference is that the overall storage requirements were reducedthanks to the camera's clever mapping techniques.

The other method uses a procedure called irrelevancy. Thismethodology automatically removes digital information that isnot visible to the human eye such an infra red light.

Digital imaging is amazing yet we have only started witnessingthe revolutionary changes that are yet to come.

About the author:Warren Lynch has been shooting commercial photography since the70's. Visit his website at www.wlynch.com or just him a call at1-502-587-7722 to quote on your next project. Get his Bi-weeklyDigital Photography Tips for FREE!. Subscribe to "The DailyDigital Dose" Now. www.photopheed.com