All you need to know about Memory Cards

Memory cards are the main format used to store and exchange digital data: MP3 music files, photos and personal content such as word files, contact lists etc. Today you will find memory card ‘slots’ in digital cameras, mobile phones, MP3 players, PDAs, notebook computers and many more devices. This overview should help you make sense of the various options available to you in the market today.

Flash Memory. Although of all memory card types only ‘Compact Flash’ cards actually bear the name, all memory cards (and sticks) are based on Flash technology. Many other devices such as USB Flash drives and MP3 players use Flash memory. However, as our focus is on memory cards, the various types of Flash cards we can discern today are:

• Secure Digital (SD/SDHC/SDXC)
• MicroSD (and MicroSDHC)
• Compact Flash
• Memory Stick (Memory Stick Duo, Memory Stick ProDuo, Memory Stick Pro-HG)
• xD Photo Card
• Micro Drive
• Multi Media Card
• Smart Media

Secure Digital cards (SD / SDHC / SDXC)
Secure Digital or SD cards are much smaller than Compact Flash cards and were originally often found in smaller devices such as mobile phones and MP3 players, but have now become the most used option in compact digital cameras. SD cards offer up 2Gb/4gb at speeds of up to 20Mb/second. SDHC cards offer sizes between 4Gb+ and 32Gb, while SDXC cards offers sizes between 32Gb and 128Gb! It's important to check that your camera supports SDXC before buying as not all cameras support it (yet) - you may also need to update your PC to support SDXC (Update available from Windows). Eye-Fi cards have built in Wi-Fi, making it possible to transfer images straight from the camera, even if the camera doesn't have Wi-Fi built in, although the camera does need to support the card for it to work. See our Eye-Fi review. Samsung also offer waterproof, shockproof, magnet proof, xray proof and dustproof memory cards, in both SD and MicroSD formats, with a 10 year warranty.

Find out which SD cards are the quickest here.

Buy Online - Common sizes available: 4gb SDHC, 8gb SDHC, 16gb SDHC Samsung Waterproof / Shockproof / Dustproof High Speed: 8gb Extreme SHDC, 16gb Extreme SDHC. Professional / High Capacity: 32gb Lexar SDHC, 64gb Lexar SDXC, 128gb Lexar SDXC.

MicroSD (MicroSDHC)
These are often used in mobile phones / smartphones and compact cameras. They are extremely small, as you can see above - this makes them more suited to mobile phones or cameras where you don't plan on removing or swapping the card. They often come with a MicroSD to SD adapter so you can use them in normal SD cameras or readers. Like SD, they also have Class speed ratings (see below).

Buy Online - Common sizes available: 4gb SDHC. 8gb SDHC. 16gb SDHC. Samsung Waterproof / Shockproof / Dustproof High Speed: 8gb Extreme. Professional / High Capactity: 32gb Lexar. 64gb Sandisk Ultra SDXC.

Compact Flash cards (CF)
Compact Flash or CF cards are popular in devices that can spare a bit more space inside, as despite their name, Compact Flash cards are among the largest cards in terms of physical size. Compact Flash cards offer a significant range of speeds and capacities, up to 64Gb and 45Mb/second – but more about speeds and capacities later. Important to note is that Compact Flash cards come as type I cards and type II. Type II cards typically allow higher storage capacities but are also physically a much thicker card. When buying a CF card, it is therefore important that you check which type of CF card your device supports.

Buy Online - Professional / High Capacity: 8gb Lexar, 16gb Lexar, 32gb Lexar, 64gb Sandisk Extreme.

Memory Stick
Memory Sticks (MS) were developed by Sony, to provide flexible storage for many of their products. Memory sticks are found in a variety of devices and offer great versatility – but unfortunately there's a lot of confusion as well, as Memory Sticks have appeared in a number of different formats. Physically speaking, there is the standard Memory Stick, this was joined by Memory Stick Duo (now discontinued), Memory Stick PRO, Memory Stick PRO-HG and Memory Stick Micro M2 which is shorter and thinner. There are also differences in the ‘controller’ software on various Memory Sticks.

Memory Stick Duo came as a standard MS Duo or an MS Duo Pro (sometimes also called Pro Duo). MS Duo Pro often came with an adapter that let you use the MS Duo Pro as an MS Pro – the controller software was the same.

Memory Stick PRO-HG is designed for high-speed data transfer based with Memory Stick PRO format technology and Memory Stick PRO-HG Duo media can also be used with Memory Stick PRO compatible products. More recently Sony has supported both SD/SDHC and Sony Memory sticks in their cameras.

Buy Online - Common sizes available: 4gb Sandisk, 8gb Sony Pro-HG, 16gb Sony Pro-HG, 32Gb Lexar.

To summarise:
Memory Stick or Memory Stick Duo (same controller different format)
Memory Stick Pro or Memory Stick Duo Pro (same controller different format)
Memory Stick Pro-HG (high speed)
Memory Stick Micro M2 (currently used more on mobile phone technology)

Note 1: Users often wonder if their device, which their manual states supports either Memory Stick or Memory Stick Duo, will also accept MS Pro or MS Duo Pro, so that they can take advantage of the larger capacities available in the ‘Pro’ sticks (See capacity below). Unfortunately the answer to that is ‘no’, because fo the different types of controller between the standard and Pro items.
Note 2: Some companies continue to launch faster and faster Memory Stick products, resulting in additional nomenclature such as MS Extreme and MS Ultra – which are compatible with MS Pro devices.

xD Picture Card (xD)
xD (Picture) card slots are found in (older) Fuji and Olympus cameras, as the cards were developed by these companies. xD cards are often sold under license and therefore you may sometimes find a different brand on the packaging, but a Fuji or Olympus branded card inside. xD cards have a distinctive, shield style design and are roughly the size of your thumb. Storage capacity can be anything from 8Mb to 2Gb.

Buy Online: Olympus xD Type M+ 2gb

There are three types of xD picture card available: Standard, Type M and Type H. The Standard cards have a maximum capacity of 512Mb but as higher resolution cameras have appeared, these cards simply don't cut the mustard.

In 2005, Fuji and Olympus released the first Type M card using Multi-level cell (MLC) technology to increase capacity and they can go upto 2Gb, but these cards suffer from slow write speeds. Type H cards are a faster write speed than the Type M, and have the same maximum capacity as the Type H, but the speed is still not as fast as the original, smaller capacity cards.

The main problem with these cards is that they are not always compatible with older card readers or cameras and Olympus also have a Panoramic feature on their cameras which can only be recorded to Olympus cards. Olympus added the Type M+ to their range of xD picture cards. Type M+ is claimed to have a write speed 1.5x faster than regular Type M.

In 2009 Fujifilm stopped supporting XD card, switching instead to SD cards, and in 2010 Olympus followed suite and announced the switch to SD memory cards.

MicroDrive (MD)
IBM developed a miniature tape drive called the MicroDrive with the physical dimensions of a Compact Flash type II card. MicroDrives are comparatively rare and if your device supports the format it should say so explictely in your user manual. MicroDrives come in 170Mb, 340Mb and 1Gb capacities.

Multi Media cards (MMC)
There often is some confusion around MMC cards as they have exactly the same physical format as SD cards. Many devices will support both formats – but not all. Despite some dealers telling customers not to worry when buying either card, please ensure that your device supports both types of card before you buy, or otherwise simply purchase the card it says it will.

Smart Media (SM)
Like CF cards, Smart Media cards are rather large, square but thin cards which, very distinctively, have a large gold ‘chip’ on the front. SmartMedia cards is no longer common and was used mainly in earlier digital cameras from Olympus and Fuji with capacities up to 128Mb.

Speed
A common question is whether or not a camera or other device will support a certain speed, for instance a 30X card. The answer to this is that modern cameras have the ability to support far higher speeds than any card you might be able to purchase today. Therefore, if speed is of importance, you can safely buy the fastest card you wish to afford.

Card speed is often stated in ‘Times’ speed (8X, 20X etc.) and sometimes, more specifically, in Megabyte per second - reflecting the card’s per-second ability to have data transferred from or to it:

Speed	Class	Transfer Rate
8X		1.2 Mb/sec
12X		1.8 Mb/sec
20X	Class 2	2.0 Mb/sec
25X		3.8 Mb/sec
30X	Class 4	4.0 Mb/sec
40X	Class 6	6.0 Mb/sec
60X		9.0 Mb/sec
66X	Class 10	10.0 Mb/sec
80X		12.0 Mb/sec
133x		20.0 Mb/sec
266x		40.0 Mb/sec
300x		45.0 Mb/sec

Capacity
The following table illustrates commonly available capacities per card type. Please note that technology progresses so fast that larger capacities become available almost every few months, whilst smaller capacities become obsolete (e.g. 16Mb and soon 32Mb).

	CF-I	CF-II	SD	MMC	xD	MS	MS Pro Duo	MS Pro-HG Duo	MS Micro
8Mb	X		X	X	X	X
16Mb	X		X	X	X	X
32Mb	X		X	X	X	X		X
64Mb	X		X	X	X	X		X
128Mb	X		X	X	X	X		X	X
256Mb	X	X	X	X	X	X		X	X
512Mb	X	X	X	X	X	X	X	X	X
1Gb	X	X	X	X	X	X	X	X	X
2Gb	X	X	X	X	X	X	X	X	X
4Gb	X	X	X			X	X	X	X
8Gb	X	X	X			X	X	X	X
16Gb	X		X				X	X
32Gb	X		X				X
64Gb	X		X

X Becoming obsolete, X Available today, X Most popular capacities, X Just launched/be launched soon

Approximate Number of Images per Capacity

Camera type	File Size	32Mb	64Mb	128Mb	256Mb	512Mb	1Gb	2Gb	4Gb	8Gb	16Gb
2mp	900Kb	35	71	142	284	568	1137	2275	4551	9102	18204
3mp	1.2Mb	26	53	106	213	426	853	1706	3413	6826	13652
4mp	2Mb	16	32	64	128	256	512	1024	2048	4096	8192
5mp	2.5Mb	12	25	51	102	204	409	819	1638	3276	6552
6mp	3.2Mb	10	20	40	80	160	320	640	1280	2560	5120
8mp	4Mb	8	16	32	64	128	256	512	1024	2048	4096
10mp	5.3Mb	6	12	25	51	102	204	409	819	1638	3276
12mp	5.7Mb	5	10	20	40	80	160	320	640	1280	2560

 

Note: 1Gb = 1024Mb

Layers
Finally a very short note on ‘layers’. As mentioned, memory cards contain ‘controllers’ – software that managed the storage and retreival of data. The quality, capacity, speed, energy-efficiency and longevity of a memory card depends on its materials, and the architecture of its controller software. So called single-layer cards are usually more expensive but offer superior energy efficiency, longevity and speed than multi-layer cards.

Longevity
Apart from the fact that technology leads us to ever growing capacities and speeds and therefore sometimes rendering certain card sizes such as 16Mb or 32Mb obsolete, it is worthwile to note that memory cards have a limited life expectancy. Again there is a difference; single layer cards may allow in excess of maybe 100,000 read-write actions, whilst multi-layer cards may only allow around 10,000 to 15,000.

This article was updated September 2011.