What is a Memory Card?
by Jonathan Fessler

What is a Memory Card?

Types of Memory Cards

Memory Card Reader/Writers and Card Adapters

Helpful References

Comparison Chart of Common Memory Cards

What is a Memory Card?

A Memory Card is a removable device used in digital cameras to store the images captured by the camera. There are several different types of memory cards available including Compact Flash, SmartMedia, and Memory Stick to name a few. Memory cards come in a range of storage capacities starting as low as 2 Megabytes (MB) to as much as 1 Gigabyte (GB). For the most part, these memory cards use a type of memory called Flash Memory (sometimes called "Flash RAM") - it is a type of nonvolatile memory that can be erased and reprogrammed in units of memory called blocks. Flash memory derives its name because the microchip is organized so that a section of memory cells are erased in a single action or "flash."

By incorporating removable memory cards, digital cameras gain several advantages over earlier models that had only built-in memory. The first advantage is that the memory of the camera can be upgraded simply by purchasing additional memory cards. The second advantage is that the user is not limited to the camera's interface to transfer the files to the computer; the camera interface is often fairly slow, requires that the user connect a cable to the port on the computer which is often hard to get at, and can sometimes be difficult to set up. Instead, the camera user can use a card reader/writer to transfer the files to the computer, or take advantage of the PC Card slot often found on notebook computers to transfer the files. After the images have been transferred to the computer or are no longer needed, the card can be erased and reused. Though there are several different types of memory cards that are currently used by camera manufacturers, all of the different types of cards do the same basic job - store data.

Types of Memory Cards

The PC Card (also known as a PCMCIA card) is one of the earliest types of memory cards that were used in digital cameras. The PC Card was originally developed to provide expandable system memory for portable computers, and was also a media used to load programs on to early portable computers. Because this type of memory card is fairly large, its use limited the ability of camera makers to produce small digital cameras, The PC Card also used a lot of power. Cameras that used these memory cards had to have large batteries and in addition, used the batteries up very quickly. The PC Card is a very common type of card, which is still used in laptop computers as a means to add functions such as modems, Ethernet and SCSI interfaces, and for transferring large files between computers. It also tends to be very durable, and is well shielded from electromagnetic fields by it's metal casing.

The PC Card comes in three different types - Type I, Type II and Type III. The Type I & II cards are solid state type memory cards (i.e. they store the information on memory chips) while the Type III cards are usually tiny hard drives. All three card types measure the same length and width and use the same 68-pin connector. The only difference between card types is thickness. The thicknesses are 3.3, 5.0, and 10.5 millimeters for Type I, Type II, and Type III cards respectively. Because they differ only in thickness, a thinner card can be used in a thicker slot, but a thicker card can not be used in a thinner slot. The Type III cards have been slowly disappearing from the market over the past few years or so and it is currently difficult to find these cards in retail outlets.

The CompactFlash memory card was developed soon after the PC Card, and in many ways is simply a smaller version of the PC Card. This was the first type of memory card that was developed with the intention of being used in digital cameras. The compact flash memory card has all of the same advantages as the PC Card, but because it is smaller, allows camera makers to design more compact digital cameras. The CompactFlash Card has several downsides, including a fairly high cost of approximately 65 cents per megabyte and relatively slow data transfer rates. However, the CompactFlash Card is now available with higher data transfer speeds allowing for faster data transfer to the computer through a card reader, and better performance form many digital cameras - especially the professional models. High Speed cards are currently available form brands such as Lexar and Sandisk at a cost typically around 70 cents per megabyte. The CompactFlash card is currently the most common type of memory card used in digital cameras, and is compatible with all current professional digital cameras.

The Compact Flash Type II, or more commonly known as the Microdrive Card, is similar in size to the Compact Flash card discussed above, but is a bit thicker, This is not a solid state memory card, but actually contains a tiny hard drive. These cards are available in very large capacities (currently up to 1 GB) and are fairly inexpensive at a cost of less than 30 cents per megabyte. A significant problem with this type of memory card is their lack of durability. Though the card is well shielded from magnetic or electromagnetic fields, they are fairly sensitive to impact and vibration and can be damaged if dropped or jarred. They also do not tolerate drastic changes in temperature well.

The SmartMedia memory card (sometimes referred to as an SSFDC - Solid State Floppy Disc Card) is a more recent product which became commonly available in the mid 1990's. This memory card is smaller and much thinner than the Compact Flash card. Due to it's smaller size, camera makers were able to begin developing even smaller digital cameras that were similar in size to some of the smallest point and shoot film cameras. The SmartMedia Cards are also more efficient with regards to power drain, and the batteries in the digital cameras that use this type of card tend to last a bit longer. Another advantage of this card type is that they are a bit less expensive to produce than CompactFlash cards with a typical cost of under 60 cents per megabyte. There are some drawbacks to the SmartMedia card system. One problem is that the cards have no shielding, so they are susceptible to data loss and damage from electromagnetic fields (such as airport x-rays). Also, these cards are not as widely compatible as the other types of memory cards - Particularly CompactFlash cards. CompactFlash cards have a control circuit built right into the memory card. This circuit allows the card to "tell" the camera or computer how much capacity it contains so the camera or computer can take advantage of all the available memory. The SmartMedia Cards do not have this controller circuit, so the memory controller needs to be built into the camera. What this means to the user, is that the camera you purchase will not be able to read any cards of larger capacity than was available when the camera was released. For example, say you purchased an Olympus D-600L camera. This camera was released in early 1998 when the largest SmartMedia card available was 16MB. Because the Controller chip in the camera was designed for 16MB cards, you cannot use cards larger than 16MB capacity in this camera - larger capacity cards will not be recognized by the Olympus D-600L camera.

The Memory Stick Memory card was developed by Sony and was first used in Sony digital cameras in 1998. The Memory Stick memory card is well shielded and durable like the Compact Flash cards but is much smaller to allow it to be used in smaller products such as ultra compact digital cameras, and MPEG players. At this time, the Memory Stick is used mostly with Sony products, but there are now several digital photo products from other manufacturers that accept the Memory Stick cards. There is also a version of this card with copyright protection technology called the MagicGate Memory Stick. This card is a bit more expensive than the standard Memory Stick card, but that additional cost pays for the potential royalty fees when recording copyrighted MPEG music.

The MultiMedia Card (MMC) was developed to try and incorporate the best features of SmartMedia and Compact Flash cards in to one system. This memory card system is very similar to the Memory Stick card with regard to its capabilities but is a non-proprietary form. The MultiMedia Card has become fairly common in products such as ultra compact digital cameras, PDA (Personal Digital Assistant) units, cell phones and MPEG players. These cards cost about the same as the Compact Flash type cards at a typical cost of slightly more than 60 cents per Megabyte.

The Secure Digital (SD) Card is similar to the MultiMedia Card in appearance and is cross-compatible with the MultiMedia card. It is a highly secure stamp-sized flash memory card with cryptographic security for copyrighted data based on proven security concepts from DVD audio. Jointly developed by Matsushita Electronic (best known for its Panasonic brand name products), Sandisk and Toshiba, the SD Card maintains a high transfer rate for fast copy/download. It also exhibits low power consumption to maximize battery life in small portable devices, Making it a good choice for digital cameras and other portable digital devices such as MPEG Players and cell phones. The Secure Digital Card is distinguishable from the MultiMedia Card by the user selectable mechanical write protect switch on the exterior card casing.

Developed by Fujifilm and Olympus, and manufactured by Toshiba Corporation, the xD-Picture Card is a high-capacity flash memory format for digital cameras. The xD-Picture Card is currently the smallest storage format of its kind on the market - comparable in size to a penny, measuring just 0.79" x 0.98" x 0.07" and weighing less than one-tenth of an ounce - with the potential for up to 8GB storage capacity in a single card. Currently though, the xD-Picture card is available in capacities up to 128MB, with a 256MB card planned to be available soon. This unprecedented combination of small size and large capacity will allow Fujifilm and other companies to manufacture sleeker and lighter digital cameras than ever before. Both Fujifilm and Olympus have begun to offer cameras compatible with the xD-Picture Card. In addition, the xD-Picture Card was designed to minimize power consumption, saving battery life and with fast read/write capabilities for smoother digital camera operation. PCMCIA and CompactFlash adapters are beginning to be available, allowing use of xD-Picture card in a variety of cameras and other devices from multiple manufacturers. The name "xD-Picture Card" was inspired by "eXtreme Digital", suggesting the excellence of this new memory media for recording, storing, and transporting audiovisual information.

Memory Card Reader/Writers and Card Adapters

A major advantage of using removable memory cards in digital cameras (besides the potential for expansion) is the ability to transfer files to your computer without having to connect the camera to your computer by a cable. To transfer your files to the computer without going through the camera, you may need to purchase a card reader/writer. Card readers are available with slots for all of the current memory cards and use a variety of computer interfaces. One card reader that I recommend highly is from Lexar and is called the Universal Card Reader. This card reader has a USB interface and 2 slots - one for SmartMedia cards and one for PC cards. It comes with a Compact Flash Type I to PC Card adapter and it is possible to purchase card adapters for most of the other memory card types that are currently available. You could also purchase a card reader that is designed specifically for the type of memory card you are currently using. Microtech makes a series of card readers called the ZiO! readers. These readers have a USB interface and are available for Compact Flash Type I & Type II, SmartMedia, Memory Stick and MultiMedia Cards. Because the ZiO! card readers will read only one type of card; they are much less expensive than most other card readers. If your computer does not have a USB port, card readers are also available with Parallel, SCSI, and FireWire interface.

If you currently own a notebook computer, you probably have a card reader already. It is the PC card slot that is usually found on the side of your notebook computer. This card slot is usually for PC Card Type II or Type III cards and is often where the modem or network interface is installed. To use this slot as a card reader, you will need to purchase an appropriate card adapter and insert your memory card with the adapter into the card slot. When the computer recognizes the memory card, it should show up as a hard drive. Then, all you need to do is simply drag and drop your image files to a folder on your computer hard drive, and you are done. The PC Card slot is usually much faster than the camera interface or a card reader for transferring the files. Card adapters are available for just about every memory card type on the market.

There is one other option that is available for SmartMedia, MultiMedia and Memory Stick type memory cards, It is the FlashPath Floppy Disk Adapter. This device allows you to transfer the files from your memory card using the floppy disk drive on your computer. The FlashPath adapter looks like a floppy disk. You insert the memory card into the adapter and then put the adapter into your floppy disk drive. You can now view the files on the floppy drive of your computer and drag-and drop the files to your hard drive. This device does not usually work on laptop computers or external floppy drives, and is very slow. However, for the computer novice, it is the easiest way to get the files in to your computer.

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Helpful References

Apple Computer
http://www.apple.com

CompactFlash Association
http://www.compactflash.org/

EE Times
http://www.eetimes.com/

IDC North America
http://www.idc.com/

Memory Stick Information For Developers
http://www.memorystick.org/e-index.html

Olympus Corporation
http://www.olympusamerica.com/cpg_section/cpg_xd.asp

PCMCIA - Personal Computer Memory Card International Association
http://www.pc-card.com/
http://www.pc-card.com/smartmedia.htm

SD Card Association
http://www.sdcard.org/

Solid State Floppy Disk Card (SSFDC) Forum
http://www.ssfdc.or.jp/english/

Sony Corporation
http://www.sony.com

Toshiba Corporation
http://www.toshiba.com

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Comparison Chart of Common Memory Cards

Memory Card Type	Standard Symbol	Capacity Range (as of 08/01)	Advantages	Disadvantages	Camera Brands Which Use Card
PC Card (PCMCIA)		8MB-1GB	• Well Shielded • High Capacity • Established Industry Standard	• High Power Drain • Expensive	• Kodak Pro Cameras • Older cameras by many brands
Compact Flash (Type I)		4MB-512MB	• Well Shielded • High Capacity • Established Industry Standard	• High Power Drain • Expensive	• Kodak • Nikon • Canon • Minolta
Compact Flash (Type II)		170MB-1GB	• Well Shielded • High Capacity • Inexpensive	• Delicate • Limited compatibility	• Canon • Nikon • Many pro cameras
SmartMedia (SSFDC)		4MB-128MB	• Small • Low Power drain • Inexpensive	• Poorly shielded • Limited Capacity	• Fuji • Olympus
Multimedia		4MB-128MB	• Small • Well Shielded • Low Power drain • Versatile	• Limited Capacity • Limited Availability	• Hitachi • Yashica
Memory Stick		4MB-128MB	• Small • Well Shielded • Low Power Drain	• Limited Capacity • Proprietary to Sony Products	Sony

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