It is important to understand the basics of a digital camera, especially terms like pixel, pixel count, white balance, sensor, sensitivity, optical zoom, digital zoom etc. These improve your understanding of digital photography, and can help you become a better photographer.
A pixel is the basic unit of measurement used to define a digital photograph. The more the number of pixels per square inch the higher is the clarity or resolution of a digital picture. Each pixel is made up of three color channels – red, green and blue -- and has a numerical value of between 0 and 255.
The makers of digital cameras use the term pixel count to describe their cameras. A camera that can shoot images whose pixel count is one million is categorized as 1 MP or one million pixel camera. These are the low-end cameras, used by beginners. The high-end cameras used by professionals range from 14MP to 22MP. The pixel count in these cameras is as high as 14 million or 22 million per image.
The pixel count also decides the size of a print in case you want to print photographs. A 3MP camera can provide excellent 4x6 inch prints, while a 4 or 5MP digital camera can deliver high quality 8x10 inch prints.
Another important term is digital sensor. A typical digital camera may have a digital sensor element that is as big as a small finger nail. Most 5MP digital cameras use a sensor that is 7mm x 5mm in size. This is much smaller than the size of the negative of a 35 mm camera. However, high-end digital cameras have large sensors, and generate superior images.
With a digital camera you can pick the white balance to suit the light source. This is meant to ensure that white looks white and not yellow, or blue. Normally your digital camera will do this automatically. You can also set the white balance yourself for better effect.
Digital cameras also have sensitivity settings similar to ISO ratings on film. Most digital cameras will have settings for sensitivity equivalent to ISO 100 and ISO 200. Many also have a setting for ISO 400. A few expensive digital SLR cameras with large sensors have settings for ISO 3200 or even for ISO 6400.
Most digital cameras also have an optical and a digital zoom. An optical zoom lens works by changing the focal length and magnification as it is zoomed. Image quality remains high. Digital zoom works by cropping the image to a smaller size. The cropped image is enlarged to fill the frame, causing a significant loss of quality.
Since each pixel generates three bytes of data, a photographer using a 3MP camera will need a storage space of 9 million bytes or 9MB to store a single image. This is a huge amount of space. Camera companies therefore allow for a compression of image using a format called JPEG. This reduces the file size significantly but while doing so a lot of data is lost. To overcome this problem companies have come up with different storage formats. Canon calls it RAW while Nikon calls it NEF. The data loss is less in these formats.