Rather than moving parts, memory cards have banks of memory registers that hold their state - on and off - without needing power, yet are easily changed. When an image is written to them, the registers are rapidly flipped on or off according to the data they must hold. To read off the memory, the registers are turned into a stream of data bits. Modern cards hold vast amounts of information and can read or write very rapidly.
For a time, it seemed that there would be just three types of digital image memory cards. Unfortunately, there are now several systems all vying for pole position. For the photographer, the main consideration is compatibility between personal equipment: if you own only one camera, there is no problem, you can download images directly to your computer. But as soon as you have another camera or you want to use another device, you must ensure compatibility. In this respect, the most versatile memory card is the CompactFlash. But cards from other manufacturers promise higher transfer rates, or better capacity, economy or size.
All cards have to be slotted into the camera so that recorded images can be saved onto them. The first time you use one, it may have to be formatted by the camera. Unlike film, you can remove the card at any stage before it is full and slot it into a reader to transfer files to a computer. You can also erase images at any time to make room for more. However, do not try to remove the card while the camera or reader is accessing it. Wait for the lights indicating card activity to go out before removing the card.
Card Care:
- Keep memory cards well away from magnetic fields, such as magnets, television monitors, audio speakers, and so on.
- Keep cards cool, do not leave them in a car on a hot day or lying around in bright sunshine.
- Keep cards dry, do not take them out into warm, humid conditions, immediately after coming out of an air conditioned room.
- Insert memory cards into cameras or card readers gently. Too much force may damage the contacts.
- Keep memory cards dust free, the contacts are extremely fine and can easily be damaged by small particles of dirt or grit.
- Keep cards in protective cases when not in use.
