CompactFlash Cards

CompactFlash cards, thankfully, are pretty easy to compare and decipher thanks to fairly meaningful speed ratings. While I'm not saying a card rated "300x" will actually reach 300x speeds -- or even that "300x" means much of anything in terms of conveying speed -- relative to other cards it's a reasonable gauge of performance. (Skip the technobabble, I want to see the scientific tests.)

Today, UDMA cards rule the roost. UDMA (Ultra Direct Memory Access) is basically the same file transfer protocol as used in modern IDE hard drives, while older CompactFlash cards used the PIO (Programmed Input/Output) protocols of early IDE drives. This is all a bunch of geekspeak for saying they've made the cards faster.

But like all things, there is a catch. True geeks will remember when IDE hard drives used a 40-pin cable; newer drives use an 80-pin cable. With CompactFlash cards, it's "kind of" the same -- to get true UDMA speeds from a UDMA card, you can't use a run-of-the-mill card reader; you need one that supports the faster, UDMA protocols. We'll see that in action in my speed demonstrations.

Write Speeds

There wasn't much point examining write speeds before the advent of UDMA-enabled cameras, and the Nikon D300 is the first. The results here were somewhat surprising, revealing a dramatic difference across brands that is not observed when looking at read speeds (see below). At least from my observations, the original UDMA CF card - the SanDisk Extreme IV - is the fastest for writing by far.

The chart below shows the number of JPG-Fine frames recorded by the D300 before the frame rate dropped below the maximum of 8 fps; as well as the throughput for recording a full buffer burst (17-18 frames) in RAW, 12-bit, lossless compression mode.

Buffer size was the limiting factor for RAW shooting, as only the SanDisk Extreme IV was able to achieve more than 17 frames (18) before frame rate dropped below 8 fps. Note how no card is able to touch the Extreme IV or PNY cards, although the Lexar shows notable speed over the others. When it comes to write speed, UDMA are most certainly NOT created equal!

Readers

Another factor in card readers is the basic interface technology used by the reader in getting the data to/from the computer (which is separate from that used getting data to/from the card). There are four basic flavors: USB 1.x, USB 2.0, Firewire 400, and Firewire 800. USB 1.x (pfftt! phooey!) is horrible and nasty -- read SLOW -- except for things like working with old-fashioned IDE hard drives (this means older CF cards, too). USB 2.0 has two speed settings, both of which fall in the Big Fat Lie category. Big Fat Lie #1 is "Full Speed," which would imply you are getting speed that is full (as in, can't get bigger) but in fact is only "full" from the old USB 1.x perspective. In other words, a device running at "USB 2.0 Full Speed" is really running at USB 1.x Pfft! Phooey! speed (technically 12 MB/sec). Big Fat Lie #2 is that USB 2.0 High Speed allows transfer of up to 480 MB/sec. Ladies & gentlemen, NOTHING runs at 480 MB/sec. This is in the same Big Fat Lie category as Hyundai making their speedometers go up to 120 MPH. You ain't getting there by any legal means.

These Big Fat Lies enable manufacturers of USB card readers to produce all sorts of absolute rubbish and fool everyone into thinking they are getting some sort of magic speed boost because they use a "USB 2.0" card reader. Absolute rubbish (in case you missed it the first time). Don't rely on such estimations for a sense of real transfer speed.

Firewire is a little different. It was invented by Apple Computer, and everyone knows they are the good guys and never lie. Firewire 400 supports, yes, 400 MB/sec transfer speeds and Firewire 800 supports 800 MB/sec. These numbers are still inflated but not so inflated as to reach Big Fat Lie status. In reality, a Firewire 400 anything will almost always be significantly faster than a USB 2.0 High Speed 480 MB/sec anything. A Firewire 800 anything will be even faster, that is, once you go out and buy a completely new $2,000 computer capable of handling the new Firewire 800 ports.