It is rare to see film cameras these days. It seems that everybody has converted from film to digital cameras and also everybody is using digital cameras in new ways such as on their cell phone. But many times there is still a need to print the digital photos on paper.
Digital photos are virtual data. In the real physical world digital photos are not different than any other computer digital file. Digital photos are a collection of bits stored on magnetic or other media. Bits are the smallest unit of computer digital data. A bit can have only two values also know are zero or when. Two bits put side by side can have four values. Three bits can have eight values, four sixteen and so on and so on. Using bits computers can represent any number.
Digital photos are a collection of pixels that when put side by side create an illusion of a continuous color photos. The more pixels in a single photo the better the illusion is. Pixels are in essence a tiny area on the photo that has a color and intensity. Each pixel can thus be represented as a series of a few numbers. For example most digital photos use the red green blue system to represent a pixel. By mixing the base colors red green and blue in different proportions every other color can be created.
A pixel is then stored by a computer as three values representing the amount of red the amount of green and the amount of blue for that pixel. Computer screen for example can later on use that information in order to display true physical world colors on a computer screen. So if a pixel can be represented by three numbers a complete digital photo can be represented by the number of pixels in it multiplied by three. In most implementation two hundred fifty six values of each red green and blue are used for sufficiently creating one of sixteen million colors and intensity combination for each pixel. Two hundred fifty six values require eight bits and thus each pixel occupies the storage of twenty four bits.
Digital bits physical representation can be very simple or very complex depending on the digital media used. Many years ago for example paper cards where used to store data. Each card had a tiny area reserved for each bit. If the area had a hole in it the bit had a zero value otherwise it had a one value. Obviously such implementation had many problems just to mention two storage capacity was very limited and data could not be easily erased.
Modern digital media almost always uses magnetic surfaces to represent bits. A magnetic sensitive coating is applied to a disk. A magnetic read write head can then change the magnetic polarity on tiny areas of the disk each polarity representing one bit value of zero or one. Such magnetic storage can achieve very high capacities and can obviously be erased and rewritten many times.
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