The Need For Speed: Compact Flash Card Transfer Analysis

Do you feel the need for speed?
Do you feel the need for speed?

Most of my cameras utilize Compact Flash (CF) cards. When you’re shooting lots of images, or capturing big files (D800), you want to be able to move data quickly. CF cards continue to gain speed (Lexar announced a 3333x CF card this week at CES). I currently have 16GB UDMA 7 CF cards (SanDisk Extreme), but there are faster ones out there if you’re willing to spend the money. While a fast card is certainly going to help you clear your camera buffer faster, I’ve found that the real speed gain comes on the image transfer side.

Interfaces

You can transfer your images to your computer either by connecting the camera or via a dedicated card reader. I’ve always preferred the card reader method, as it is less cumbersome and I don’t need to use my camera battery to do it. When it comes to speed, you’ll want to choose a card reader that supports UDMA high-speed cards. Beyond that, there are really only a few other factors that can affect your data transfer speeds:

  • Card Speed
  • Interface (i.e. USB vs. Firewire)
  • Target Disk speed

I compared three different interfaces (USB 2.0, USB 3.0 and Firewire 800) across four different target drives using a UDMA 7 SanDisk Extreme CF card. For the Firewire test, I used a SanDisk FW 800 card reader. For both USB tests, I used a Hoodman RAW Steel USB 3.0 card reader. Since my Mac Pro 2010 did not natively include USB 3.0, I am able to test via the built-in USB 2.0 bus, and USB 3.0 via a CalDigit USB 3 PCIe expansion card.

Target Drives

I tested the same CF card across four different destination drives

To keep the test parameters uniform, I used the same UDMA 7 CF card with 1800 MB worth of NEFs from my Nikon D4. I used the same USB cable for both the USB 2.0 and USB 3.0 testing. My computer is a 2010 Mac Pro tower utilizing 6 3.33 GHz processor cores and running OS X 10.9.1 Mavericks. I used Photo Mechanic to perform a “real-world” transfer scenario. Each NEF received basic IPTC updates during the transfer, just as would my normal image files.

Results

I timed each data transfer and then converted to a data rate of megabytes per second (MB/sec). I’ve presented my results in a chart, below. USB 2.0 data transfers were the slowest overall; with an average transfer speed of 26.4 MB/s. The Firewire 800 interface, was 1.7x faster than USB 2.0, with an average speed of 45.4 MB/s. The fastest transfers were with the USB 3.0 interface, which averaged 63.4 MB/s. That’s 2.4x faster than USB 2.0 and 1.4x faster than Firewire 800.

A comparison of CF data transfer rates using three different interfaces and four different drive types (click to enlarge).
A comparison of CF data transfer rates using three different interfaces and four different drive types (click to enlarge).

Effect of Destination Drive Type

Looking at the performance chart, you can see that in most cases, the OWC Mercury Accelsior SSD blade delivered the fastest transfer times. The one exception was over USB 2.0, where I got a slightly faster speed with my 3G SSD. That’s probably within the margin of error of me using my stopwatch on these tests. The SSD blade was clearly the fastest when used with a USB 3.0 card reader. In all, the overall transfer rates to SATA drives was fairly similar within an interface type.

Conclusions

It’s clear that you’ll get the fastest transfers when using a UDMA-enabled USB 3.0 card reader. While transferring files to an SSD also increases speed, you’ll see a bigger boost by moving from USB 2.0 to USB 3.0. The price of solid-state drives isn’t really practical for mass-storage, either. I use my SSD for my boot partition and to host my Lightroom catalog. PC users probably never had a Firewire interface on their computer, but many Mac users will. If you have a new Mac that has USB 3.0 on it, you might consider getting a new card reader that will take advantage of that speed. Based on my results, downloading a full 16GB card to a standard internal drive will take over 10 minutes via USB 2.0, just under six minutes with FW800, or about 4 minutes with USB 3.0. Of course, some of this will depend on your CF card’s rated speed, too. Faster CF cards should deliver faster transfer speeds. Mac Pro users who want to add USB 3.0 should consider the CalDigit USB 3/eSATA card. I’ve tried other cards that didn’t function well.

2 thoughts on “The Need For Speed: Compact Flash Card Transfer Analysis”

  1. Apropos the use of Compact Flash cards:
    Have you any experience with using the newer, faster CF cards in a RAID array on your Mac? I have been looking into the most economical/stable method to hook up a RAID to backup my growing photo catalog. As we all buy newer/faster CF cards it seems those older – still good – cards might work in a RAID setup. Alas, I don’t have the computer chops to do this myself so am looking for suggestions (if you have any!) Most all of the light google searching I have done is older, archived material or refers to PCs.

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