Want CNET to notify you of price drops and the latest stories?

CompactFlash allies rally against dominant SD

Ninety-five percent of cameras today use Secure Digital memory cards. So why do CompactFlash allies think their format still stands a chance?

Stephen Shankland principal writer
Stephen Shankland has been a reporter at CNET since 1998 and writes about processors, digital photography, AI, quantum computing, computer science, materials science, supercomputers, drones, browsers, 3D printing, USB, and new computing technology in general. He has a soft spot in his heart for standards groups and I/O interfaces. His first big scoop was about radioactive cat poop.
Expertise processors, semiconductors, web browsers, quantum computing, supercomputers, AI, 3D printing, drones, computer science, physics, programming, materials science, USB, UWB, Android, digital photography, science Credentials
  • I've been covering the technology industry for 24 years and was a science writer for five years before that. I've got deep expertise in microprocessors, digital photography, computer hardware and software, internet standards, web technology, and other dee
Stephen Shankland
6 min read

In the flash-memory format wars, Secure Digital has vanquished xD Card and Memory Stick. SD, as it's known, is supported by everything from Apple laptops to Panasonic 3D videocameras.

Transcend has begun selling 400X and 600X CompactFlash cards with capacities up to 64GB and 32GB, respectively.
Transcend has begun selling 600X and 400X CompactFlash cards with capacities up to 32GB and 64GB, respectively. Faster, bigger sequels are under development. Transcend

But CompactFlash, a rival flash-card format that prevails in high-end SLRs from Canon, Nikon, and Sony, is holding out. More than that: its backers are developing a high-performance successor. Nikon, Sony, and memory card maker SanDisk have proposed that the CompactFlash Association standardize a sequel that can transfer data at a rate of 500MB per second and reach eventual capacities of 6TB.

"This next-generation format is expected to be widely adapted to various products, including those other than high-end digital SLRs," Shigeto Kanda, a Canon executive and chairman of the CompactFlash Association board, said in a recent statement.

The technical specifications are important. But there's evidence that photographers are willing to keep CompactFlash alive for a much more mundane reason: size.

In electronics, miniaturization is almost the law of the land. Manufacturers work to shave each tenth of a millimeter off their phones, laptops, music players, and compact cameras. SD cards are small, and microSD and miniSD variations are even smaller.

Perversely, it's the greater bulk of CompactFlash that appeals to many photographers.

"It's quite amazing how small and light (and fast) SD cards are, but the size is actually too small," said Mark Gillespie of GHP Studio. "SD cards are just too small to be juggling around in a fast-paced situation--easy to drop, hard to find."

Adds Nicole Young, who shoots with both CompactFlash and SD, "The main reason I like CF cards is because of their bulkiness...I have lost a few [SD cards] in the past and then randomly found them in a side pocket of my laptop bag. They're just so little, and almost paper-thin so they're easy to misplace."

Mainstream momentum
Market economics are on the side of SD, though.

"The vast majority of cameras--more than 95 percent--now only use SD cards," said InfoTrends analyst Ed Lee.

SD has also made inroads into CompactFlash's stronghold: digital SLR cameras. Where lower-end models from leaders Canon and Nikon once used CompactFlash, they now come equipped with SD slots. Even high-end models such as Canon's 1D Mark IV and 1Ds Mark III have an SD slot alongside their CompactFlash slots. That can be handy in a pinch because mainstream SD cards are a lot easier to buy or borrow.

CompactFlash, which once came in compact cameras such as Canon's PowerShot S30, isn't likely to stage a mainstream resurgence, said IDC analyst Christopher Chute.

"CompactFlash is destined for niche markets. According to our data, about 5 percent of current dSLR photographers are classified as 'pro,' with many of them being newly minted, former 'prosumers' who are buying pro equipment and shooting for money part time. And they are shooting with [Canon] 5D Mark II, 7D, [Nikon] D300s, which use CompactFlash."

But a niche can still be a reasonable business--just ask Porsche about cars or IBM about mainframes.

When it comes to photography, the CompactFlash allies could have several demanding requirements in mind.

First is the challenge of shooting bursts of photos, a perpetual concern as camera resolution and, therefore file sizes, increase. Professional photographers need cameras that will keep pace, for example, from one collection of shots of an athlete crossing a finish line to another burst shortly afterward.

Video is another new requirement. Today's cards aren't taxed overmuch by SLR video, even at 1080p resolution, but tomorrow's cameras likely will go beyond that with higher data-recording rates, higher quality, higher frame rates, and higher resolution. Cameras from cinema specialist Red record video in a higher-quality raw format that requires much higher storage capacity and data-writing rates.

And the 1920x1080 resolution of 1080p video is small compared with what a lot of cinema customers prefer: so-called 4K resolution with each frame 4,000 pixels wide. That's about four times the number of pixels as 1080p video.

"The next 'big thing' once the 3D hype ends is 4K," Chute said. "The CompactFlash Association guys are looking at professional video as a burgeoning market that will transition over from tape to CF, and it looks like Canon will move in that direction too."

And that, fundamentally, will be the most likely factor to influence CompactFlash's future. People buy cameras primarily for other reasons than memory card formats, and manufacturer support is what will keep the format relevant.

Dueling roadmaps
SD, of course, has a strong future before it. It's evolved from the original SD specification, which had a 4GB limit, to SDHC (Secure Digital High Capacity) with a 32GB limit, and the newer SDXC (Secure Digital Extended Capacity) with support for up to 2 terabytes.

The SD Card Association revealed plans to triple SD card data transfer speeds at this fall's IFA electronics show. The new specification should arrive in 2011, with products supporting it in 2012. Stephen Shankland/CNET

The SD Card Association--the consortium that oversees the technology--is working on faster speeds, too. In September, the group announced that it is working on an SD card improvement that will triple data-transfer speeds to 300MB/sec by adding new electrical contacts. That variation is expected to arrive in the market in 2012.

Today's top-end CompactFlash cards can transfer data at 90MB/sec. The new CF 6.0 version of the specification that was completed in November will reach 167MB/sec.

CompactFlash today relies on the same communication standard as hard drives, but the format is living in the past in a way. Where hard drives have moved to a faster data-transfer technology called Serial ATA (SATA), CompactFlash still uses the older Parallel ATA (PATA). Today's fastest CompactFlash cards use a version called Ultra Direct Memory Access (UDMA) Mode 6, and the CF 6.0 cards will use UDMA Mode 7.

A CompactFlash sequel proposed by Nikon, Sony, and SanDisk will go beyond that by using PCI Express (PCIe) technology. "The increased speeds will enable imaging and video applications that could not be accomplished using the current CompactFlash specification's Parallel ATA interface," the companies said.

By going with PCIe, they'll ditch hard-drive technology altogether. This means that another contender for next-generation CompactFlash tech for cameras--a SATA-based variation of CompactFlash called CFast--likely will be relegated only to industrial uses such as slot machines and trains.

The CFast successor to today's CompactFlash memory card standard, shown here in prototype form, was spurned by the camera industry.
The proposed CFast successor to today's CompactFlash memory card standard, shown here in prototype form, was spurned by the camera industry. Stephen Shankland/CNET

"CFast is a high-speed format but it was optimized for industrial/embedded applications, where it's starting to see some adoption," the CompactFlash Association said in a statement. "The proposed next-generation memory-card format [with PCIe] has been optimized for dSLR and high-performance video applications."

PCIe technology is another data transfer mechanism that's used to connect network cards and all kinds of other devices to computers. PCIe is a serial interface, meaning that it transfers ones and zeros at a high speed along a relatively small number of wires. Parallel bus interfaces, such as today's CompactFlash and the earlier non-Express version of PCI, used more wires, with signals traveling down them in sync.

Computing industry lessons
Curiously, that's the same approach used by Fusion-io, a storage start-up that's trying to leapfrog the idea of SATA for PCIe-attached flash memory. It's aimed at servers, though, not electronics devices.

Richard Kaufmann, an avid photographer who happens to be a longtime server expert at Hewlett-Packard as his day job, said PCIe is great for transferring data but raises a concern. "Cramming a lot of bandwidth through a small number of wires is more power consuming than spreading that bandwidth over more wires," he said.

Ultimately, he envisions a day when cameras have vast amounts of built-in memory, perhaps augmented by removable cards. That approach would let the camera maker optimize memory layout for minimal power consumption, he said. And in the nearer term, he likes the idea of multiple SD slots. With four slots configured as today's servers use RAID arrays of hard drives, such an approach could boost both transfer speeds and data reliability.

Regardless of how the camera industry gets there, faster transfer speeds are important.

"Transfer speed is something that does matter," Gillespie said. "It can take quite awhile to download [photos from] a whole event or wedding--45 minutes--and at midnight the thought of another 15 minutes to download the last card can make you want to risk it and just go home."