About camera memory cards

Like many things digital memory cards come in all shapes and sizes, but they all serve the same purpose which is to store images. It’s fairly common to see a particular camera support a number of different cards, be it through multiple card slots or by variations of a common format, though this is in constant state of change as manufacturers drop support for some in order to adopt others.

Memory cards are used to store information from cameras and other devices. They are based on flash memory, a non-volatile form of memory which means no power is required to store data recorded to it. Over the past few years, they have brought increased capacities and better performance, all the while slowly dropping in cost, to the point where even a standard card can happily record thousands of print-quality images. But not all cards are created equal; the one you need will depend on the camera you are using, and even then there will be a wide choice available to you.

Memory card speeds

Aside from their physical differences, perhaps the most confusing aspect of different memory cards is their speed. Some cards quote speeds in megabytes per second (MBPS), while others simply use the ‘x’ suffix (such as 150x speed, for example). To add to the confusion, some only list a ‘class’ of card. So how can they be compared? Well, 1x is equivalent to 150kbps, a system which stems from from the classification of CD-ROMs. Therefore, a 10x speed is (roughly) equivalent to 1.5MBPS, a 100x speed is equivalent to 15MBPS and so on.

The Class system, meanwhile, which is used on SD media formats, is fairly easy to understand as the quoted figure directly relates to the minimum transfer speed of the card. So, a Class 2 card offers a minimum transfer rate of 2MBPS, a Class 4 cards offers 4MBPS and so on. This does depend partly on how fragmented the card is; a formatted card will be able to have data written to it much more efficiently than one with a number of images already stored on it.

Transferring images to a computer

Although it’s possible to connect a camera to a computer in order to transfer images from a memory card, a far better solution is to invest in a separate card reader as this doesn’t require you to use a camera (thus preserving its battery). These can also be found relatively cheaply and can read a number of different cards at the same time, simply through the USB or firewire port on your computer.

The main types of memory card:

sdhc memory cardSecure Digital (SD)

The majority of cameras record images and movies to one or more varieties of SD memory card. These are small, postage-stamp sized cards, which can be found cheaply – often for just a few pounds online.

Although standard SD cards suffice for everyday use, by today’s standards they are fairly slow in terms of transfer rates, and have been largely superseded by the SDHC format (HC denoting ‘high capacity’).

This newer range of memory cards boasts capacities from 4GB to 32GB, along with an increase in speed and performance, despite keeping to the same dimensions as the previous SD cards. As such, devices which accept SDHC cards are backward compatible with the older SD format (though, sadly, not the other way round).

sdxc memory cardSDXC cards

SDXC cards represents the latest generation of SD media. Although the format is still in its infancy, cards have already been released with 32GB and 64GB capacities, which is set to rise to a staggering 2TB in the next few years.

Demand for them has come mainly from the rise in high-definition video capture, which has proliferated across compacts and DSLRs and video cameras.

While prices now are still very much on the high side, and only a handful of consumer devices able to accept them, the next few years are likely to see more compatible products and prices drop to a more affordable level.

Micro and Mini SD cards, Micro SDHC and Mini SDHC

Micro and Mini SD cards, as well as Micro SDHC and Mini SDHC varieties, also exist. These are designed for smaller devices such as mobile phones, portable media players and satellite navigation systems.

Mini SD cards offer the same performance and benefits of standard SD cards, but are able to do so in a smaller form. Micro SD cards, meanwhile, still manage to offer high capacities (with MicroSDHC cards matching the 32GB capacity of standard SDHC cards) but in a card no larger than a fingernail. It is also possible to use an SD adapter to facilitate the use of Mini and Micro SD cards in standard SD card slots, which is particularly useful when transferring images to a computer or other device.

compactflash memory cardCompactFlash (CF)

Although many DSLRs have adopted the SD formats, professional DSLRs maintain support for CompactFlash media.

CF cards are larger and stronger than SD cards, and more suitable for use in adverse conditions (some professional cards claim to offer shock protection and usability in temperatures as low as -25°C and up to 85°C).

Although the format has shown more consistency in its offerings than others, cards fall into one of two varieties: Type I and Type II. The only physical difference between the two is in the latter being slightly thicker, and although the majority of cameras support both types, almost all current cards conform to the Type 1 specification. Some cameras have also recently dropped support for Type 2 cards.

udma memory cardUltra Direct Memory Access (UDMA) cards

Many high-performance CompactFlash cards are also based on Ultra Direct Memory Access (UDMA) technology, whose main benefit is higher transfer rates to and from the card.

Virtually all recent cameras supporting ComapctFlash storage also support UDMA cards – those which don’t will still accept these, but the benefits of UDMA technology will not be fully realised. Likewise, only UDMA card readers are able to support the faster transfer rates of such cards.


Like SD memory cards, CompactFlash cards now also have a new high-performance sibling dubbed CFast. Based on Serial ATA technology (SATA), these cards are capable of both increasing storage capacity and offering far faster transfer speeds (almost three times faster than current CompactFlash cards can manage).

xd memory cardXD memory card

Olympus and Fujifilm cameras have long used the xD format for image storage, with capacities of up to 2GB currently available.

For a number of years, however, Fujifilm has supported the more common and rapidly evolving SD formats alongside this, with Olympus recently following suit, to the point where the xD-compliant products are in a significant minority.

As such, it looks increasingly likely that the format will play a lesser part – if one at all – in future cameras and other electronic devices.

Memory stickMemory stick

The Memory Stick is Sony’s own proprietary media format, used across its range of electronic devices.

As with the SD format is has seen a number of revisions throughout its lifetime to enable faster transfer rates and higher capacities, and it has followed a similar path in offering a Micro versions and a more recent ‘XC’ format (the latter offering similar specifications to the SDXC format).

Although the range continues to evolve, Sony has also begun to adopt SD cards across a range of its products, strengthening the dominant position of SD media for electronic devices.

Tips for buying a memory card

1. Think carefully about how much memory you need. A 2GB or 4GB card should suffice for most applications, though if you are recording high-definition movies you may want to consider a larger card, or two smaller ones.

2. Your camera may have a small lamp which indicates when the card is still in use – never take a memory card out of a camera while images are still being recorded to it.

3. Many digital memory cards come with generous warranties – sometimes covering the card’s working lifetime – while technical support may also typically be offered.

4. Look out for memory cards which come bundled with image recovery software, as this may help retrieve any images should you accidentally delete them.

5. The price of memory cards varies a great deal between retailers, and shopping online is often the  the best way to find a bargain. Counterfeit cards, however, are known to be in circulation, so it’s important that you only buy from a reputable retailer.