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[nextpage title=”Introduction”]
Digital cameras have been using a memory card system for storing photos for quite some time now. The cameras store photos as jpg files (or in another format, depending on the camera), and all that has to be done is to transfer the card’s contents to your computer’s hard disk to be able to see a photo, edit it or print it out. At the time when digital cameras came onto the market, the only way to connect them to a computer was through a serial port, an extremely slow process. Currently, digital cameras can be connected to the computer’s USB port, providing a faster file transfer rate.
There are several formats of memory card on the market, seeing that the major digital camera makers, instead of following a single joint standard, opted for setting up individual standards. The most outstanding ones are Compact Flash (CF), Memory Stick (MS), MultiMediaCard (MMC), Secure Digital (SD), SmartMedia (SM) and xD.
In this tutorial we will explain in details the technical differences of each one of the leading memory cards standards, since they are not compatible among them. It is important to note that the difference is not on the physical side. An important aspect of cards is their transfer rate or speed. With a faster transfer rate you can not only the files faster to your computer but also when shooting pictures the camera can be ready faster for you to take your next snapshot. Since each camera model uses one type of card, the type of memory card the camera uses can be a very important aspect when buying your digital camera. Power consumption can play a relevant role on battery life and is an aspect one should pay also attention.
Capacity is also one of the most important features of a memory card. Keep in mind that with older standards like MultiMediaCard and SmartMedia you won’t be able to use high-capacity cards (above 256 MB) because they simply don’t exist for these standards. We will be discussing that on our tutorial as well.
Before going ahead, you may want to take a look at the following table. This is a table to help you to choose the memory card size for your camera, based on its resolution, in megapixels. “File size” means the average file size using camera’s “high-resolution” JPEG mode. The actual number of images per card will vary and depends on the camera model and complexity of the scene being photographed. The number on each row indicated the number of pictures a given memory card can hold at a given resolution. For exemple, a 128 MB memory card can hold approximately 106 pictures using 3 megapixel resolution.

Approximate Number of Images per Capacity
Camera Type:	File Size	32 MB	64 MB	128 MB	256 MB	512 MB	1 GB	2 GB	4 GB
2 Megapixel Camera:	900KB	35	71	142	284	568	1,137	2,275	4,551
3 Megapixel Camera:	1.2MB	26	53	106	213	426	853	1,706	3,413
4 Megapixel Camera:	2MB	16	32	64	128	256	512	1,024	2,048
5 Megapixel Camera:	2.5MB	12	25	51	102	204	409	819	1,638
6 Megapixel Camera:	3.2MB	10	20	40	80	160	320	640	1,280

[nextpage title=”CompactFlash (CF)”]

CompactFlash is the most popular and oldest (was first introduced in 1994) memory card type. Cameras from Canon, Casio, Epson, HP, Kodak, LG, Minolta, NEC, Nikon, Panasonic, Phillips, Polaroid and others use this kind of memory card.

Figure 1: CompactFlash (CF) card.

CF cards can be found in several speed options. A “1x” CompactFlash card transfers data at 150 KB/s. Thus, the data transfer rate of a 16x card is 2.4 MB/s (150 KB/s x 16 = 2,400 KB/s). The only problem is that manufacturers don’t say if this transfer rate is for reading or writing. Since read transfer rate is higher than write transfer rate, we think these numbers refer to the read transfer rate.
For the professional market, there are CompactFlash cards with Write Acceleration Technology (WA) tecnology, which provides an extra performance at the same speed grade. For example, a 80x Compact Flash with this tecnology can be up to 23% faster than standard 80x cards. To use this technology, however, your camera must support it. So far only professional cameras from Kodak (all professional models), Nikon (D1x, D1h, D2h and D-100), Pentax (*ist D), Olympus (E1), Sanyo (DSC-MZ3) and Sigma (SD-9 and SD-10) support this kind of memory card. If you install a WA-enabled CompactFlash on a regular camera it will work as a regular CompactFlash card.
Besides the speed advantage, another biggest advantages of the CF cards is that this format is so far the only one that have capacities over 1 GB. You can find CF cards up to 8 GB!
You can find CompactFlash cards in two sizes, Type I and Type II. The only difference between them is the card thickness. CF Type I cards can be installed in both Type I and Type II CF slots, while Type II CF cards only fit Type II slots.
It is very interesting to observe that CF interface is based on PCMCIA (PC Card), but using 50 pins instead of 68. So you can install a CF card directly into a PCMCIA slot on you laptop using a very simple pin adapter. Because of that you can find on the market cards called CF I/O, that are modems, network adapters and other peripherals that use the CompactFlash size, to be installed on laptops or other devices.
Main specs

• Available Capacities: 64 MB, 128 MB, 256 MB, 512 MB, 1 GB, 2 GB, 4 GB and 8 GB
• Transfer Rate: 1x = 150 KB/s, 4x = 600 KB/s, 12x = 1.8 MB/s, 16x = 2.4 MB/s, 32x = 4.8 MB/s, 40x = 6.0 MB/s, 80x = 12 MB/s
• Voltage: 3.3V or 5V
• Power consumption at High Performance: 65 mA at 5V or 50 mA at 3.3V
• Length: 1.43 in (36.4 mm)
• Width: 1.68 in (42.8 mm)
• Height (Type I): 0.13 in (3.3 mm)
• Height (Type II): 0.19 in (5.5 mm)
• Shock: 50Gs @ 11ms
• Vibration: 15 Gs peak to peak
• Operating temperature: 0º C to 60º C (32º F to 140º F)
• Non-operating temperature: -20º C to 85º C (-4º F to 185º F)
• Humidity: 5% to 96%
• For more information: https://www.compactflash.org

[nextpage title=”Memory Stick (MS)”]
Developed by Sony and used in Sony products, like digital cameras and MP3 players. Only Konica Minolta and Samsung (in just a few models) also use Memory Stick.
Actually there are 5 different types of Memory Stick: Memory Stick, Memory Stick with select function, Memory Stick PRO, Memory Stick Duo and Memory Stick PRO Duo. The three first models have the same size, while the Duo models are smaller, but can be installed in Memory Stick slots by using an adapter.

Figure 2: Memory stick specs.

Figure 3: Memory Stick PRO and Memory Stick with memory select.

The PRO models (developed together with SanDisk) are faster and are available with larger capacities, up to 1 GB (technically PRO cards can have up to 32 GB). The device (digital camera) must clearly state it is compatible with PRO models to accept these kind of cards, because even though it has the same size as the original Memory Stick, it has twice the number of pins used in the connection with the camera.
Memory stick with select function provides Memory Stick cards with larger capacities for cameras that don’t accept the PRO model. The card has a small switch on its back were you can choose the “memory bank” you will use. For instance, if you have a 256 MB Memory Stick with select function it works as if it was two separated 128 MB Memory Sticks.
The Duo models were designed to be used in devices that need copyright protection, like MP3 players. The copyright protection circuit is called MagicGate. Memory Stick PRO also has this circuit, but OpenMG Jukebox and SonicStage software aren’t compatible with Memory Stick PRO, only with Duo models.
Main specs

• Available Capacities (Memory Stick): 4 MB, 8 MB, 16 MB, 32 MB, 64 MB, 128 MB and 256 MB
• Available Capacities (Memory Stick PRO): 256 MB, 512 MB and 1 GB (technically can have up to 32 GB)
• Average transfer rate (Memory Stick): 350 KB/s
• Maximum transfer rate (Memory Stick): 2.45 MB/s
• Maximum transfer rate (Memory Stick PRO): 20 MB/s (160 Mbps)
• Minimum write speed (Memory Stick PRO): 1.875 MB/s (15 Mbps)
• Voltage: 2.7 V to 3.6 V
• Power consumption: 4.5 mA (average for Memory Stick), 20 mA (average for Memory Stick PRO) and 130µA (standby)
• Length: 1.97 in (50 mm)
• Width: 0.84 in (21.45 mm)
• Height: 0.11 in (2.8 mm)
• Length (Duo models): 1.22 in (31 mm)
• Width (Duo models): 0.79 in (20 mm)
• Height (Duo models): 0.063 in (1.6 mm)
• Weight: 0.14 oz (4 g)
• Operating temperature: -5º C to 65º C (23º F to 149º F)
• Storage temperature: -40º C to 100º C (-40º F to 212º F)
• Shock: 150 Gs @ 10ms
• Vibration: 15 Gs peak to peak 5% to 90% C
• For more information: https://www.memorystick.org/

[nextpage title=”MultiMediaCard (MMC)”]
MultiMediaCard standard was introduced in 1997 and is used by companies such as HP, Nokia and Samsung. A new size was recently released, called RS-MMC, which stands for Reduced Size MMC and is a smaller MMC card. It can fit the original MMC slot by the use of an adapter.

Figure 4: MultiMediaCard (MMC).

Figure 5: RS-MMC card.

Recently a new standard called MultiMediaCard Plus (a.k.a. MMC+, MMC Plus or MMC 4.0) was released, providing a higher speed rate.
Main Specs

• Available Capacities (MMC): 32 MB, 64 MB and 128 MB
• Available Capacities (RS-MMC): 128 MB, 256 MB and 512 MB
• Available Capacities (MMC+): 256 MB, 512 MB and 1 GB
• Read speed (MMC and RS-MMC): 2 MB/s
• Read speed (MMC+): 11 MB/s
• Write speed (MMC): 1 MB/s
• Write speed (RS-MMC): 2 MB/s
• Write speed (MMC+): 7 MB/s
• Voltage: 2.7 V to 3.6 V
• Power Consumption: < 33mA (read), < 35mA (write) and < 50µA (standby)
• Length (MMC): 1.26 in (32 mm)
• Length (RS-MMC): 0.71 in (18 mm)
• Width: 0.94 in (24 mm)
• Height: 0.05 in (1.4 mm)
• Weight: 0.05 oz max (1.5 g max)
• Operating temperature: -25º C to 85º C (-13º F to 185º F)
• Storage  temperature: -40º C to 85º C (-40º F to 185º F)
• Shock: 1000G max
• Vibration: 15G peak-to-peak max
• Humidity: 8% to 95%
• For more information: https://www.mmca.org/

[nextpage title=”Secure Digital (SD)”]
Secure Digital standard was originally developed by Matsushita (Panasonic), SanDisk and Toshiba in 2001 and is based on MultiMediaCard standard.

Figure 6: Secure Digital (SD) card.

Secure Digital cards were originally intended to protect the music industry by using rights management and copy-protection scheme from a group called SDMI (Secure Digital Music Initiative), hence its name. Funny enough, the SDMI specification was cracked shortly after it was released and the SDMI group no longer exists.
There is a smaller SD card called MiniSD, developed to be used on cell phones, which can be installed on SD slots using an adapter.

Figure 7: MiniSD card.

On SD slots you can use other kind of devices besides memory cards. These devices, called SDIO, can be modems, Bluetooth antennas, Wi-Fi (IEEE 802.11) antennas, GPS, etc.
As it occurs with CompactFlash, Secure Digital cards can be found in several transfer speed grades. An “1x” card has a transfer speed of 150 KB/s, the same unit used by CF cards, so you can compare SD speeds to CF speeds directly. A 32x card has a transfer speed of 4.8 MB/s on both SD and CF standards, for example. The same way as it occurs to CF, SD cards manufacturers don’t specify if this speed is for reading or writing. Since write speeds are lower than read speeds, we think the transfer rate refers to the card read speed.
Main specs

• Available Capacities: 32 MB, 64 MB, 128 MB, 256 MB, 512 MB and 1 GB
• Voltage: 2.7 V to 3.6 V
• Power Consumption: < 33mA (read), < 35mA (write) and 100µA (standby)
• Read speed: 12 MB/s
• Write speed: 1x = 150 KB/s, 32x = 4.8 MB/s, 40x = 6.0 MB/s
• Length (SD): 1.26 in (32 mm)
• Width (SD): 0.94 in (24 mm)
• Height (SD): 0.082 in (2.1 mm)
• Weight (SD): 0.070 oz max (2 g max)
• Length (MiniSD): 0.85 in (21.5 mm)
• Width (MiniSD): 0.79 in (20 mm)
• Height (MiniSD): 0.055 in (1.4 mm)
• Weight (MiniSD): 0.035 oz max (1 g max)
• Operating temperature: -25º C to 85º C  (-13º F to 185º F)
• Storage  temperature: -40º C to 85º C  (-40º F to 185º F)
• Shock: 1000G max
• Vibration: 15G peak-to-peak max
• Humidity: 8% to 95%
• For more information: https://www.sdcard.org

[nextpage title=”SmartMedia (SM)”]
Originally developed by Toshiba in 1995, SmartMedia is another memory card standard that you can find. It was first called SSFDC (Solid State Floppy Disk Controller). If you pay attention, it really looks like a small floppy disk, hence its original name.

Figure 8: SmartMedia (SM) card.

Main specs

• Available Capacities: 16 MB, 32 MB, 64 MB and 128 MB
• Transfer rate: 2.5 MB/s
• Length: 1.8 in (45 mm)
• Width: 1.5 in (37 mm)
• Height: 0.03 in (0.76 mm)
• Weight: 0.07 oz (2 g)
• For more information: https://www.ssfdc.or.jp/english/

[nextpage title=”xD (eXtreme Digital)”]
xD (eXtreme Digital) is a memory card format developed by Olympus and Fujifilm in 2002 and originally produced by Toshiba. These three companies are owners of the “xD” trademark. It was developed to replace SmartMedia – it is smaller and have higher capacity.

Figure 9: xD memory card.

Figure 10: Comparison between xD and SmartMedia (SM) memory cards.

Main specs

• Available Capacities: 32 MB, 64 MB, 128 MB, 256 MB, 512 MB and 1 GB (technically can have up to 8 GB)
• Transfer speed: 5 MB/s
• Write speed: 1.3 MB/s (16 MB and 32 MB cards) or 3 MB/s (64 MB and up cards)
• Length: 0.98 in (25 mm)
• Width: 0.79 in (20 mm)
• Height: 0.067 in (1.7 mm)
• Weight: 0.07 oz (2 g)
• For more information: https://www.olympusamerica.com/cpg_section/cpg_xd.asp

[nextpage title=”Summary”]
Having several memory cards types available is simply too much. In our opinion on the long run only four standards will be alive: CF, MS PRO, SD and xD. MultiMediaCard (MMC) and SmartMedia (SM) are pretty dead right now, specially because of their very low transfer rate. In fact, xD was created to replace SmartMedia (SM) and SecureDigital (SD) was created to replace MultiMediaCard (MMC). MS has a low transfer rate compared to newer standards, but Sony pushes this standard really hard, so we will be seeing Memory Stick alive for some years, until it is completely replaced by MemoryStick PRO, which provides a really good transfer speed.