With traditional cameras, the film is used both to record and store the image. With digital cameras, separate devices perform these two functions. The image is captured by the image sensor, then stored in the camera on a storage device of some kind. In this section we look at many of the storage devices currently being used.

Removable vs. fixed storage

Older and less expensive cameras have built-in fixed storage that can't be removed or increased. This greatly reduces the number of photos you can take before having to erase them to make room for new ones.

Almost all newer digital cameras use some form of removable storage media, usually flash memory cards, but occasionally small hard disks, and even the venerable floppy disk. Whatever its form, removable media let's you remove one storage device when it's full and insert another. The number of images you can take is limited only by the number of storage devices you have and the capacity of each.

The number of images that you can store in a camera depends on a variety of factors including:

The capacity of the storage device (expressed in Megabytes). The resolution at which the pictures are taken. The amount of compression used.

The number you can store is important because once you reach the limit you have no choice but to quit taking pictures or erase some existing ones to make room for new ones. How much storage capacity you need depends partly on what you use the camera for. If you're used to shooting 5 or 6 rolls of standard film on vacation, your camera better be able to store the same number of images or you'll be out of luck.

Removable storage

Since both flash memory cards and magnetic disks are widely used in digital cameras, let's pause here to look briefly at how these very different forms of storage compare. Both types of storage devices share some outstanding features:

They are erasable and reusable. They are usually removable, so you can remove one and plug in another so storage is limited only by the number of devices you have They can be removed from the camera and plugged into the computer or printer to transfer the images. Despite their similarities, they also have some significant differences: Magnetic disks have moving parts while flash memory cards don't. Magnetic disks are usually cheaper (per picture) and faster. Flash memory cards are smaller, lighter, and less prone to damage.

Let's take a look at the leading types of image storage devices in digital cameras.

Flash memory cards

As the popularity of digital cameras and other handheld devices has increased, so has the need for small, inexpensive memory devices. The type that's caught on is flash memory which uses solid state chips to store your image files. Although flash memory chips are similar to the RAM chips used inside your computer there is one important difference. They require no batteries and don't loose images when the power is turned off. Your photographs are retained indefinitely without any power to the flash memory components. These chips are packaged inside a case equipped with electrical connectors and the sealed unit is called a card.

Flash memory cards consume little power, take up little space, and are very rugged. They are also very convenient; you can carry lot's of them with you and change them as needed (assuming you can afford lots of them).

Types of flash cards

There is an old set up line for a joke that begins "I have good news and bad news." The good news is that we have these flash memory cards at all. The bad news is that they come in a variety of formats that are not interchangeable. Once you have a sizable investment in memory cards, you are locked into using only those cameras that support your format.

Until recently, most flash cards have been in the standard PC Card (PCMCIA) format that is widely used with notebook computers. However, with the growth of the digital camera and other markets, a number of smaller formats have been introduced. As a result of the competition, cameras support a confusing variety of incompatible flash memory cards including (but as the lawyers say "not limited to") the following:

PC Cards CompactFlash SmartMedia MemorySticks Multimedia Cards

Each of these formats is supported by its own group of companies and has its own following. If one will ever prevail over the others remains to be seen.

PC Cards (ATA)

When laptop computers became popular, they didn't have room for large storage devices so small plug-in cards were developed. Initially called PCMCIA cards (after the Personal Computer Memory Card International Association), this name was later changed to PC Cards. However, not everyone has switched to the new name so the cards are now called by two names!

Whatever you call these devices, they are used in most notebook computers and some cameras. About the size of a credit card, PC Cards come in a variety of types or thicknesses, but it's the Type I and II cards that are used for solid state, or flash memory. Like CompactFlash and SmartMedia, PC Cards are ATA compatible so they can be swapped between devices and systems. (Any ATA-compatible card will work with any ATA-compatible system, including digital cameras and almost all computers.) These cards currently store up to 1.2 Gigabytes.

CompactFlash cards

CompactFlash was developed by SanDisk Corp and uses the popular ATA architecture that emulates a hard disk drive. The cards are 1.433-inches (36.4 mm) wide by 1.685-inches (42.8 mm) long-about the size of a matchbook. At the time this was written, CompactFlash looked like the early winner in the digital camera flash memory sweepstakes. It was the most widely used form of digital camera flash memory. Type I cards (see box below) currently store up to 512 megabytes.

Compact Flash Terminology

Like many advanced technologies, CompactFlash is moving faster that the terminology used to describe it. The CompactFlash Association (CFA) is trying to standardize terminology to avoid confusion and here are the terms they recommend until a final ruling is made.

CompactFlash cards and slots that are 3.3 mm thick are called CompactFlash (abbreviated as CF) or CompactFlash Type I (abbreviated as CF-I). Note that when there is no Type I or Type II designation it implies a Type I device. CompactFlash cards and slots that are 5mm thick are called CompactFlash Type II (abbreviated as CF-II). Lexar USB enabled CompactFlash cards are referred to as USB Enabled CompactFlash. IBM Microdrives are referred to as CF+ Type II Microdrive (abbreviated as CF+/II Microdrive).

Note. CF+ originally referred to I/O cards such as modems, Ethernet cards and so on, but in the digital camera storage area, the IBM Microdrive is the only device that current warrants the name (because it utilizes a high power (current) mode). The Lexar USB Enabled CompactFlash card is sometimes referred to as a CF+ card since it has a USB (I/O) interface added to the card. Using the CF+ terminology for these different types of cards does create problems, so the CFA is working to develop recommended terminology that will be useful to users.

SmartMedia cards

SmartMedia is the major competitor to CompactFlash and is used by a number of leading camera companies. Like CompactFlash, SmartMedia is based on an ATA architecture. The major advantage of SmartMedia is its simplicity; it is nothing more than a flash chip on a card. It contains no controllers and no supporting circuitry, which reduces the size of the card as well as its manufacturing costs. The problem with this approach is that the necessary controller functions must reside in the camera and therefore compatibility with newer or older versions of the cards isn't guaranteed. A number of the first cameras using this storage medium had to be returned to their manufacturers for upgrades when the next generation of higher-capacity cards was released. These cards currently store up to 64 megabytes.

Sony Memory Sticks

Sony Corporation has developed a new form of flash memory called a Memory Stick™ that's shaped something like a stick of gum. The current versions have capacities of up to 64 Megabytes using currently available flash chips, but capacity can be increased up to 256 Megabytes by 2001 as denser chips become available.

MultiMedia cards

A MultiMediaCard weighs less than two grams and is the size of a postage stamp. Targeted initially at the mobile phone and pager markets, other markets including digital photography and MP3 music players have started to take advantage of this solid-state data storage device that's about one-fifth the size of the popular CompactFlash memory card.  

Memory Card Storage Cases

Cards are easy to misplace and the smaller they are, the easier they are to lose. If you don't find a way to store them safely, you're sure to run some through the washing machine forgotten in a shirt or pants pocket. One way to keep them safe is to use an inexpensive storage case.

Magnetic disks

Instead of flash memory, which uses solid-state chips, some cameras are designed to use magnetic disks, much like those used in your desktop system.

Floppy disks

One of the oldest and cheapest storage media still in use is the 3«-inch floppy disk. You'd be hard pressed to find a computer system that can't read these disks. There is one digital camera that has chosen this almost universally available media for its in-camera storage. Fitting a fairly large floppy disk drive into a camera increases its size a little, but the ready access to drives that can open and use the image files make up for this one shortcoming. Almost all other types of storage require special hardware or software on the machine before they'll open your image files. It's the simplicity and universal usability of the floppy disk that makes it so attractive.

It's only been a matter of time before someone introduced cameras that accepted the latest high-capacity floppy disks. Now they are beginning to appear on the market.

Hard disks

One of the current drawbacks of compact flash memory cards is their limited storage capacity. For high resolution cameras this is a real drawback. One solution is high speed, high capacity hard disk drives. Until recently, these drives were too large and expensive to be mounted inside cameras, but that changed with IBM's introduction of 1 Gigabyte, 340 Megabyte, and 170 Megabyte Microdrive hard disk drives. These drives are smaller in volume and lighter in weight than a roll of film. In fact, they are so small they can be plugged into a Type II CompactFlash slot on a digital camera or flash card reader. (Type I CompactFlash slots are thinner.) These drives will first appear in expensive professional cameras, but eventually will drift down in price to a point where they can be used in consumer cameras.

Another form of hard drive comes packaged in a Type III PC Card. A newer Type IV card will be used for high capacity hard drives.

Clik! disk drive

Iomega's Clik! drive uses a 40 megabyte 2-inch square disk. One version of the Clik! drive is designed to provide additional storage in the field. When your flash card is full, you can download the images to a battery powered Clik! mobile drive. Back at your home or office, just place the drive in its docking station that connects to the computers parallel port and download the pictures to the computer. 

Magneto Optical Disks

The iD-Photo disk that stores 730 MBytes has been developed by Olympus, Sanyo and Hitachi-Maxwell. Expect cameras with this disk to begin appearing very soon. Eventually, capacity may be increased to over 3.5 Gigabytes.

Optical discs

Although not yet adopted by a digital camera manufacturer, small recordable optical discs much like the familiar CD are on their way. DataPlay discs can hold 500 MB on a disc expected to cost somewhere around $10. The disks, like CD-R discs are write-once but that ensures archival quality with no danger of important files being deleted or written over.