|Western Digital My Passport for Mac; LaCie Rugged Mini; Seagate GoFlex Pro|
Today's DSLRs and mirrorless digital cameras provide the outdoor photographer with lots of megapixels for detailed landscapes and the ability to crop into shots of distant wildlife. But high-megapixel images take up lots of space on memory cards and hard drives. Quality-minded outdoor shooters also tend to shoot RAW images rather than JPEGs because RAW offers a number of benefits, not the least of which is better image quality. But RAW files also take up lots of space on memory cards and hard drives. And if you shoot videos, they really eat up memory.
At home, you can download your image files and store the keepers on one or more external hard drives, but those drives require AC power to operate, something you generally don't have in the field. A handy solution is a portable hard drive, which gets its power from the computer: Just plug it into the appropriate port on your laptop, and you have lots of extra memory. You can download the day's images, freeing up your memory cards for more shooting. If you're just out for the day, you can use the portable drive to store backups of what's on your memory cards, then download the cards onto your regular hard drive(s) when you get home. Or you can bring a couple of portable drives and make backups that way.
Today's portable hard drives are plug-and-play simple, and speedy, too. The most common connections for portable drives are USB 2.0 and 3.0, and FireWire 400 and 800, with the new Thunderbolt interface offering even more speed. USB (Universal Serial Bus) 2.0 Hi-Speed can transfer data at up to 480 Mbits/second, or 60 megabytes per second (8 Mbits = 1 MB). USB 3.0 SuperSpeed ups that to 5 Gbits/second, or 625 MB per second (1 Gbit = 1000 Mbits)—10 times faster. FireWire 400 can transfer data at up to 400 Mbits/second (50 MB/sec.); FireWire 800 can transfer data at up to 800 Mbits/second (100 MB/sec.). Thunderbolt can do up to 10 Gbits/second (1250 MB/sec.)—twice as fast as USB 3.0. A few portable drives use eSATA technology, which can do up to 2400 Gbits/second (300 MB/sec.). Speed is important, not just from a time standpoint, but to conserve your laptop's battery power while afield.
In real life, the actual transfer speeds will be somewhat slower than the theoretical maximums, but that still means downloading your images goes very quickly. The important thing is to get a drive with an interface that's compatible with your laptop. Note that both the drive and your computer must support the interface in order to gain maximum performance: You can attach a USB 3.0 drive to a USB 2.0 computer, but you'll get USB 2.0 speed, not USB 3.0.
Portable drives also tend to be more rugged than standard external drives, better able to withstand the rigors of travel. There are two types: solid-state, with no moving parts; and rotating, containing rotating disks like conventional hard drives. The solid-state units can better withstand shock and are smaller, but the rotating ones are faster, have higher capacities and cost less per megabyte. Rotating-type portable drives are available in capacities from 500 GB to 2 TB. For most field use, a 500 GB or two should suffice. LaCie, Seagate and Western Digital offer good lines of portable drives. Of particular interest to outdoor photographers are LaCie's Rugged Mini (available in 500 GB, 1 TB and 1.5 TB), Seagate's GoFlex Pro ultra-portable drives (500 GB, 750 GB) and Western Digital's My Passport (500 GB, 1 TB, 2 TB).