What takes priority when you buy memory cards for your camera: price, capacity or card speed? The answer will probably differ with different photographers. Cash-strapped amateur photographers are usually price-driven, while professional sports photographers will put the highest priority on card speed and be prepared to pay a premium for faster cards. Some photographers prefer having several 1GB or 2GB cards while others find it more convenient to shoot with higher capacities.
What takes priority when you buy memory cards for your camera: price, capacity or card speed? The answer will probably differ with different photographers. Cash-strapped amateur photographers are usually price-driven, while professional sports photographers will put the highest priority on card speed and be prepared to pay a premium for faster cards. Some photographers prefer having several 1GB or 2GB cards while others find it more convenient to shoot with higher capacities. With the current proliferation of brands and types, how do you decide where your priorities should be? An understanding of the marketplace – and some of the new technologies that have recently become available – will help you to make the best decision.
Card Prices High-speed cards are usually double the price, with the fastest cards claiming an even higher premium. High capacity also tended to increase CF card prices. For the highest capacity CF cards, we found a 16GB SanDisk Extreme III card priced at just under $190. (Memory Stick and xD-Picture Card media are currently more expensive than CF and SD cards.)
Memory Card Comparison Click here to view Memory Card Comparison PDF file.
Speed Ratings An alternative speed rating system identifies card speeds by a number plus ‘x’, where ‘x’ is equivalent to 150 KB/second. With the advent of SDHC (Secure Digital High Capacity) a second speed classification has appeared. The SDHC specification classified data transfer speeds on the basis of the minimum sustainable data transfer speed. Currently, three speed classes have been defined: Class 2, Class 4 and Class 6, corresponding with minimum sustainable data transfer speeds of 2MB, 4MB and 6MB per second respectively. Cameras in which these cards are used must be capable of handling the faster data transfer speed. Older cameras designed for SD cards cannot use the newer, faster SDHC cards, but SDHC-compatible cameras will take SD cards as well.
Memory Cards for DSLRs Although there are two thicknesses of CF cards – Type 1 at 3.3 mm and Type II at 5 mm – this is of little relevance as all DSLRs have the wider slots that will accept both types. Furthermore, with falling memory card prices, CF Type II cards have all but vanished from the market and Microdrives (which have the same form factor as Type II CF cards) are equally thin on the ground. While most recently-released DSLRs that use SD cards are also compatible with SHDC cards, older cameras and card readers won’t be compatible unless the manufacturer has released a firmware update to add SDHC compatibility. Similarly, many DSLRs that use CF cards don’t support the new UDMA protocol (see below) – although they will accept UDMA-enabled cards.
Do You Need a High-Speed Card? Regardless of the card’s speed rating, the camera is the key factor that influences data transfer speeds. So if your camera cannot support fast transfer speeds, there’s little point in paying extra for a super-fast card. Cameras that are UDMA compatible (see below) will be able to fully utilise the high transfer speeds of the fastest cards, although other DSLRs probably won’t. Interestingly, it is almost impossible to obtain information on data transfer speeds from any camera manufacturer covering the company’s entire range. However, most camera manufacturers publish information that allows camera users to estimate the buffer memory capacity for their cameras. All digital cameras have a dedicated buffer memory where the captured image data is held until it is processed and passed to the memory card. Buffer memory capacities vary greatly, with digicams usually having smaller buffers than DSLRs and professional DSLRs having the largest buffer memories. Once the buffer is full, continuous shooting speeds slow down to keep pace with the image processing. If your camera has a relatively small buffer memory, a fast memory card could be an advantage as it will allow data to be transferred more quickly to the memory card. However, unless your camera supports high transfer speeds, it may only add an extra shot (or maybe two) to the length of a burst. Another area where fast cards could be advantageous is for shooting video with a compact digicam. Capturing VGA video at 30 frames/second will involve transfer of roughly 10MB of data per second without sound. This increases to roughly 15MB/second for widescreen video with sound. A small buffer memory will quickly fill up at such rates so camera manufacturers often recommend using cards with at least 80x speed for shooting video.
UDMA Technology Although UDMA cards will work in any camera that can accept the card, the only way to take full advantage of the speed increase they support is to use them in a camera that is UDMA-enabled. Currently, the only cameras we’ve been able to find that fit into this category are the Canon EOS-1Ds Mark III, Nikon’s D3 and D300 models, the Olympus E-3 and Sony’s DSLR-A700. UDMA technology can provide worthwhile speed advantages in such cameras. However the main advantage of UDMA cards is to increase card-to-computer transfer rates when paired with a UDMA-enabled reader. Data will be transferred at approximately twice the speed of USB 2.0 or Firewire transfer, halving the time taken to move image files.
Card Readers Some memory cards carry no speed rating. Potential buyers must visit the manufacturer’s website for this information.
Beware of Counterfeit Cards We strongly advise that you purchase from a reputable retailer to minimise the chances of getting stuck with a ‘dud’. We also recommend buying well-known brands because the fakes can be compromised in reliability, compatibility and performance. The general rule that applies to all purchasing applies to buying memory cards: if the deal looks too good to be true, it probably is. Click here for a table (PDF) showing memory card capacities and prices, updated August 2008.
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