What happens when you take a picture… When you take a picture with a digital camera, instead of a piece of film the light strikes a digital sensor array. These digital sensors are computer chips with names like CCD, CMOS, or others. They replace the film that must be moved across the focal plane of the camera.

How are the images digitised? First the image goes through colour filters above the individual sensors. The sensor changes the image from light waves into an analog electrical signal. The analog signal then goes through an analog to digital converter, where it becomes a pure digital signal. Then it is put through a series of electronic filters that change the white balance and colours of the image. Next a compression cycle makes the image as small as possible by dumping unnecessary pixels, for more efficient storage. Now the camera has a cool digitalised image.

What happens after the digitisation? Then the image is transferred to a temporary storage area inside the camera called buffer memory, when the buffer is full, the image is written out to your storage media, such as a memory card. The buffer size in the camera is an important thing because it tells you how many images you can take in quick succession. If you have a tiny buffer in your camera, you will have to wait a bit after you take several images.

Storage of Images on a Digital Camera The most widely used type of memory card is the compact flash card (CF Card). Some of the more modern cards (such as the SmartMedia cards) for specialized cameras have recently been introduced as well, although the standard CF Card is by far the most popular and least expensive. A memory card is measured by its memory size, in megabytes (MB). The more memory the card has the more images it can hold. Thus, a 256 MB memory card will be able to hold many more images than a 32 MB memory card.

Resolution The digital sensor is made of billions of tiny sensor points called pixels, which are short for picture elements. Resolutions of digital cameras range from 0.3 megapixels to 10+ megapixels. A megapixel is just a way of expressing how many pixels are on the CCD sensor, in millions. They are laid out in an array with rows and columns and each pixel can be located in the grid by the combination of its horizontal and vertical position. For instance, take a camera which has an array of sensors in its CCD that is 3000 horizontally, and 2000 pixels vertically (3000x2000). The simple calculation 3000x2000 = 6,000,000 shows that the camera has six million pixels, so its a 6 megapixel camera.

Optical Zoom v. Digital Zoom Digital cameras usually come with two types of zoom... The first is the optical zoom which is identical to that found on traditional cameras. When using optical zoom, you can get closer to a particular object without stuffing up the image quality. Digital zoom, however, is a new type of zoom that is found only in digital cameras. When using digital zoom, the camera itself modifies the image electronically to bring the object closer to you. It does this by cropping the image and then stretch out the middle part of the image. The result of this is that photographing objects using digital zoom usually decreases the quality of the images.

Pricing of Digital Camera The price of a digital camera depends mostly on the number of mega pixels, and the size of the memory buffer. Even cheap cameras these days still produce nice images though you might be limited in the maximum picture size on photo paper, and will have to waste a bit more time when taking photos. Practically every digital camera is able to take pictures to display on the Internet, or to send as an . Images on the Internet are very low resolution -- about 72 to 100 dots per inch -- so any quality digital camera will be capable of making beautiful images for display there.