Owners of high-resolution digital cameras can definitely benefit from high-speed memory cards, as discussed in our review of the latest products (April 2006 issue of Shutterbug). But in camera speed is only one of the important aspects for anyone who shoots numerous images. Data transfer to a computer is also a significant factor and the right accessory can provide lightning-fast downloads.

All digital cameras allow for direct connection to a computer using a USB cable. That process works but it tends to be slow; with some cameras, it can be incredibly slow, as discussed later. Using the camera for downloading images also drains the batteries, unless you use an AC adapter, sometimes an extra cost option. That makes a fast memory card reader or other type of device a highly desirable alternative; indeed, an accessory of that type is often less expensive than an AC adapter for a camera.

Image Downloading Accessories
As most owners of high-resolution cameras have discovered, a memory card reader is very convenient. Connect the device to your computer's USB port and in a few seconds it will appear as a new drive. You can then keep the card reader permanently connected, ready for use at any time; no battery is required. There's no need for driver software (from the manufacturer's website) either, except with computers using Windows 98 or Mac OS 9 or older systems.

Any card reader offers convenience, but frankly, some older devices are sluggish. The more recent models, using high-speed USB 2.0 connectivity, are preferable in this respect to the older USB 1.1 models, for reasons discussed in our sidebar (below).

Owners of laptop computers may feel that they do not need a card reader because their machines include PC card slots, also called 16-bit PCMCIA CardBus slots. Buy a suitable adapter for the memory card formats that you use, and it's certainly possible to download images without a reader. Some laptops are also equipped with memory card reader slots for one or a few card formats, which can eliminate the need for an adapter.

There is one major problem in downloading through either type of built-in PC card slot--the process can be unbelievably slow. (See the data in our Performance chart.) But there's good news for laptop owners: faster devices called 32-bit CardBus memory card adapters, available from Delkin, Lexar, and Viking. These slim devices are remarkably fast and preclude the need to carry a large, bulky card reader when traveling.

How We Tested
Full scientific testing--using a vast range of different computers and memory cards--would have required a great deal of equipment and numerous hours, well beyond our resources. Consequently, I decided to proceed with practical testing: transferring image data to and from a computer. The PC used was a Compaq Pentium 4 2.8GHz laptop with a 4200 RPM hard drive, USB 2.0 ports, 512MB of RAM, and Windows XP Home OS. I consider this machine to be roughly "average" in speed and RAM memory.

In order to assess the various types of devices discussed earlier, I started with 0.95GB of Nikon D50 image files (JPEG and raw). First I copied those files to a very fast 1GB SanDisk Extreme III CompactFlash and/or a Secure Digital card. Then, I copied the same files from the card to the computer. Both processes were timed with a stopwatch and the results are listed in our Performance chart.

Note: Here's my usual disclaimer for any test of this type. The actual results would differ depending on the exact computer, memory card, and the mix of image files that were used. Consequently, the results of my tests should be viewed only as an indicator as to which products may be very fast and which may work at a snail's pace. However, it's likely that the relative performance of a device would be similar under other circumstances. In other words, an accessory that moved data at a very leisurely pace is unlikely to be fast in any test. Even so, a difference of less than 10 percent in speed should not be considered significant.

Lexar provided a sample of their Professional 4-Port USB 2.0 Hub with two Pro card readers so I also tried downloading from two memory cards simultaneously. The test results are not included in the chart because this approach did not produce any time savings. It took exactly twice as long to download data from two memory cards as from one card.

In my estimation, the primary benefit of the Lexar hub seems to be convenience. After returning from a trip with many cards full of images, you could insert four of them into individual Lexar USB 2.0 Professional readers neatly stacked on top of each other. The images would be transferred while you were reading mail or answering phone messages. Of course, you could use the same approach with any card readers hooked up to any powered USB 2.0 hub.

Note: All of the USB 2.0 card readers tested are compatible with Windows and Mac operating systems. All meet USB 2.0 specifications but are backward compatible with the older USB 1.1 ports, at the slower data transmission speed.

In addition to card readers, I also tried downloading via the computer's PC card slot. First, I tested a 16-bit CompactFlash adapter, a typically inexpensive accessory designed exactly for this purpose. (The adapter, with memory card installed, simply plugs into a laptop's PC card slot.) Then, I tried a similar device from Delkin: a 32-bit CardBus CompactFlash adapter said to be 4-6 times faster. (Lexar and Viking market a virtually identical device for CompactFlash cards only and Delkin also makes a model for five other types of memory cards.) This Delkin device called for installing software (driver) even with Windows XP; after the installation, the 32-bit adapter proved to be a fine performer.

For comparison purposes, I also tried transferring 0.95GB of image files made with a Canon EOS Digital Rebel using the Extreme III CompactFlash card. After connecting the camera to the computer with the supplied USB cable, I began timing the process. My patience ran out before the transfer (at USB 1.1 speed) was finished; after 30 minutes I discontinued the test. Some newer cameras support the USB 2.0 Hi-Speed standard and should allow for much faster direct data transfer.

Final Evaluation
All of the latest card readers were great, allowing for fast downloads. The Lexar Pro model proved to be the fastest but it's also the most expensive. Frankly, I would be happy with any of the card readers tested, but at $19, the SanDisk ImageMate offers the best value. Anyone who owns cameras that use different types of cards will probably want one of the multi-format readers because of their great versatility.

When traveling with a laptop, a 32-bit CardBus adapter--for CompactFlash or for five other types of cards--would make a fine alternative. The only problem is that the Delkin CardBus device requires driver software even for Windows XP; a CD is included but the installation process is unduly complicated. Check for Support at www.delkin.com if you encounter installation problems.

The performance difference between the "extremely fast" and "very fast" contenders in our chart is not dramatic. It would be of greatest interest to those who frequently shoot numerous high-resolution images or for pros on extremely tight deadlines. On the other hand, the frustratingly slow alternatives should be acceptable only for snap shooters who occasionally take a few low-resolution pictures. If you own a 5+ megapixel camera, you'll definitely want one of the latest image data transfer devices, available for as little as $20.

As you scan the Performance chart consider the speed of transfer from a card to a computer as the most important aspect. That's the most common application for a card reader or PC card adapter. Those accessories can also be used to transfer image data to a memory card, for moving files from one computer to another, for example. But there are more suitable devices for that purpose, the USB 2.0 flash drives. See our review of the latest models of these devices in the July 2006 issue of Shutterbug, including some with the really cool U3 Smart technology described at www.u3.com.

USB 2.0 Ports And Hubs
All of the card readers tested in this roundup are high-speed USB 2.0 models designed to provide peak performance with computers that include USB 2.0 ports. Older, USB 1.1 models are still available, too, but they're extremely slow by comparison. The theoretical maximum speed--or "target" transfer rate--for USB 1.1 is a mere 12Mbps vs. the 480Mbps for USB 2.0 connectivity. Naturally, you need to use a computer with USB 2.0 ports to take advantage of the accelerated data transfer.

If your Mac or PC has only the older USB 1.1 ports, the USB 2.0 devices will work fine, but only at the slower speed. Consider upgrading to USB 2.0 by installing a device such as the Adaptec 4-Port Card Kit ($40). That's a worthwhile investment in general, because most types of computer peripherals (including scanners and printers) now employ USB 2.0 connectivity.

If your computer is already equipped with USB 2.0 ports, you may want to buy a USB 2.0 (not an older USB 1.1) "powered" hub with at least four additional ports. That's useful for anyone who owns many peripherals with USB connectivity. An external accessory of this type, such as the Adaptec XHUB4, costs under $50.

Note: Manufacturers of some computer peripherals recommend against using a USB hub, although I have not experienced any problems with a broad variety of devices. I did not test any of the new card readers using a hub but my older SanDisk USB 2.0 multi-card reader works fine with an Adaptec USB 2.0 hub.

Lexar also makes a Professional 4-Port USB 2.0 Hub specifically for its Professional USB 2.0 CompactFlash or Secure Digital card readers. This rugged accessory ($69) was designed for connecting up to four of the "stackable" Pro card readers; it ships with special USB 2.0 cables for that purpose. Connect several of the devices and you can download from several memory cards simultaneously. (A hub is not required for connecting several of the Lexar FireWire Pro card readers because those can be daisy-chained.)

Fast Vs. Slow USB 2.0
The term "USB 2.0" is not clear cut because there are three "signaling rates" in this standard: Low Speed (1.5Mbps), Full Speed (12Mbps equal to the USB 1.1 standard), and Hi-Speed (480Mbps). A device that's marked USB 2.0 will not provide the fastest possible data transfer unless it supports the Hi-Speed standard. (Some digital cameras with a USB 2.0 rating employ only the Full Speed standard, while a few are Hi-Speed; that information may or may not be provided in the specifications.)

Note: To translate to megabytes per second, a more meaningful term for digital photographers, divide megabits by 8, thus 480Mbps equals 60 megabytes per second (MB/s).

All of the full-size card readers that I tested were Hi-Speed devices; none was dramatically slower than another. Naturally, some of the older "USB 2.0" labeled accessories on the market may support only the Full Speed standard. While I was not able to obtain a USB 2.0 Full Speed or USB 1.1 card reader for testing, I used a USB 1.1 accessory as recently as 2004. Transferring 1GB of image files from the fastest cards (40x) then available consumed about 10 minutes. The process might be a bit faster with one of today's 80x cards, but the USB 2.0 Hi-Speed devices are still significantly faster and are available at prices starting at $20.