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Tuesday, April 20, 2010

Hi-Tech Studio: Memory Requirements

CompactFlash remains the mainstay memory card for professional DSLRs. We look at speed ratings, HD video requirements and some of the current generation of pro cards.


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CompactFlash just keeps getting better and better. And where digital SLR cameras are concerned, better means faster data-transfer speeds and higher capacities. Celebrating its Sweet 16th birthday this year, CF delivers specifications that allow professional cameras—and professional photographers—to perform at their maximum capacity.

High data-transfer speed, also known as read/write speed, allows cameras to rapidly write buffered images to the CF card for permanent storage—which means you can shoot as fast as the camera was designed to shoot without a bottleneck at the storage end of the pipeline. Conversely, when it’s time to download, you can transfer images from the CF card to your computer’s hard drive in less time. When cards maxed out in the 2 to 4 GB range, that didn’t matter much. But now that 16 GB and 32 GB cards are quite common, download speed has become significant.

Most manufacturers rate their cards based on the original read/write speed of a CD-ROM, which zipped data along at 0.15 MB/s. That baseline rate is “x,” and card speeds are expressed as multiples of that speed. For example, 60x represents a sustained write/read speed of 9 MB/s (multiply 60 x 0.15 MB/s). This is the potential speed, not necessarily reality. And in some cases, it refers to top speed, not sustained speed. Also, the transfer speed rating isn’t the only factor that affects performance. Matching a high-speed card reader to high-speed cards is important if you hope to attain peak throughput.

Speed and capacity are particularly important for the current generation of multi-megapixel cameras that capture HD video in addition to large RAW files. In the SDHC card world (see sidebar), the minimum specification for satisfactory video capture is speed class 4, which equates to a 4 MB/s sustained read/write speed. This actually is a very low threshold. Nearly all CF cards currently available from name-brand manufacturers can handle HD video. But you always should opt for the fastest cards you can afford in order to ensure you’re enjoying the full speed potential when it comes to video capture, burst shooting and downloading.

The Delkin 64 GB CompactFlash Pro card is UDMA-enabled and promises sustained read/write speeds of 63 MB/s (420x). Like all UDMA cards, it delivers best performance when used with UDMA-compatible cameras and card readers. Included are a travel-safe case and a lifetime limited warranty.

The Hoodman UDMA 16 GB RAW CF card boasts a transfer rate of 675x. That equates to 100 MB/s and sets the high-water mark for CompactFlash. Hoodman memory cards are made in the USA and offer a lifetime limited warranty. Although the name includes the word “RAW,” they serve all file formats; RAW is the adjective that Hoodman uses to describe their cards’ speed. Hoodman RAW CF cards now use an SSD (solid-state drive) flash in their construction. SSD flash is among the most reliable available and is said to endure one-half-million lifecycles (one lifecycle equals a complete fill with data and a complete download).

Kingston’s 32 GB CompactFlash Ultimate 266x card offers a minimum sustained write speed rating of 266x (40 MB/s) and even higher read speeds (up to 45 MB/s). Their Ultimate line of CF cards is gaining popularity among pros because of the consistent performance and enhanced reliability. Hailed as a major player in the computer-memory arena, Kingston Technology is one of the world’s largest manufacturers of memory. They produce a variety of memory products for computers and Flash memory for digital cameras, mobile phones, MP3 players and PDAs. Kingston CF cards come with a bonus: data-recovery software from MediaRECOVER (available via download) so you can restore accidentally deleted image files.

 

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