Traditional photography uses film as a storage medium. When one film is used up, simply take it out and pop in a new one. The film is eventually developed and the stored images printed. Digital photography also has a form of removable storage – memory cards. The advantage of these cards over film is that they can be erased and reused. Images stored on memory cards can be transferred to a computer for further processing and permanent storage, or they can be transferred directly to a printer. Memory cards are not the only medium for image storage, but they are the most common. Other storage media include removable hard drives and optical disks.
Memory cards come in a variety of sizes, so you need to figure out how much storage space is required for your photos. This can vary according to the megapixel rating of your camera, the type of storage format, and the amount of compression used to store the images.
The most common type of compression is JPEG, but this is a ‘lossy’ format. This means that some of the data that makes up your image is discarded and cannot be retrieved. For most purposes, this loss of data is not critical to the quality of the image and the savings in terms of storage space more than compensate for the lost data. Sometimes, however, lossy formats are not acceptable so the image has to be stored without any compression at all. This requires significantly more storage space than JPEG.
CompactFlash is the most popular type of memory card for digital cameras. It is relatively inexpensive and is widely available. It is used by a number of different camera manufacturers, so if you buy a new camera, chances are it can use CompactFlash. There are two kinds of CompactFlash cards — Type I and Type II. Some cameras can only accept one type, so it is important to know which one you need for your camera.
Secure Digital / MultiMedia Card (SD/MMC)
SD/MMC cards are the smallest type available. SD/MMC are identical except that SD cards have a write-protect switch which prevents images from being accidentally erased. They can be used in ultracompact cameras and also in personal entertainment devices like MP3 players. SD/MMC cards have less maximum storage capacity than CompactFlash cards (currently at 1 GB) but still, offer enough space for most digital photography needs.
xD-Picture Cards are also very small — less than a 1-inch square. They were developed by Olympus and Fuji and are most commonly used in those brands of camera. They can be used in other types of cameras with a CompactFlash adapter.
Memory Stick was developed by Sony and is used in almost all Sony digital cameras. It can also be used in other Sony devices like MP3 players and PDAs. Memory Sticks are used on very few other cameras besides Sony cameras, so switching to another brand will most likely mean being unable to use this memory.
A MicroDrive is an actual hard drive housed in a CompactFlash Type II casing. Because they are mechanical drives with moving parts, they are somewhat more delicate than flash memory cards. They must be handled with care and are more prone to breakage. MicroDrives also have a slower access time than CompactFlash cards but have the advantage of larger storage capacity at cheaper prices.