By Ron Dawson
Currently, the two most wide spread “flavors” of SD cards are plain SD and SDHC. SD cards can hold up to 2GB of data, whereas SDHC cards can hold 4GB to 32GB of data. They are based on the FAT32 file system. FAT stands for File Allocation Table and it is a computer architecture structure upon which most computer operating systems and smaller memory devices are based. It is the FAT32 system that limits video clips captured on SD and CF cards to just 4GB each (approximately 12 minutes of time for most cameras).
A couple of years ago, the SDXC (secure digital extended capacity) format was introduced. This new system was based on the SD Association’s 3.0 specification and created an entirely new structure that is based on exFAT file system (also known as FAT64). These cards are NOT backwards compatible with older SD host devices. The benefit of this new format is extended data capacity and transfer buffer speeds.
Lexar has come out with its Professional SDXC card that is 64GB and 128GB with bus transfer speed of 133x, or 20MB/s. (To put this in perspective, the cards I normally shoot my gigs on are 16GB SDHC cards with 30MB/s speeds). The SDXC format is designed to hold up to 2TB of data!
I shot a series of short video clips with the card and it performed exactly as I had expected. No issues or problems. So my review isn’t so much about the performance of the card, but what you need to prepare before using it:
1. Operating systems: If you’re running on a Mac, you need OS 10.6.5 to mount an SDXC card. (Note: even after I updated to 10.6.6, the SD card slot in the side of my Intel Core i5 iMac still did not read the card. Depending on when your Mac was released, you may need to use a card reader instead of the built-in reader). If you’re running Windows, the supported operating systems are Windows 7, Vista SP2, and Windows XP (must download the exFAT patch update).
2. Formatting on your computer: Lexar recommends you use the SD 3.0 formatter as opposed to your computer’s native formatting tools. Download it at http://www.sdcard.org/consumers/formatter_3/. As of the writing of this article, there was no MacOS formatter. If your device has formatting capabilities and is SDXC compatible, you can always format the card that way.
3. Host devices: Make sure any device you use has the SDXC symbol displayed in its spec sheet to ensure proper compatibility. An SDXC-compatible device can still use SDHC or SD cards.
4. Video clip limit: I had assumed that since the card is based on the exFAT file system that I could shoot clips longer than 12 minutes (4 GB). Unfortunately, on the T2i I was using, that was not the case. After letting it run for 12 minutes, it auto-stopped.
In closing, I want to issue a word of caution. Be wise. One of the obvious benefits of the larger capacity cards is not having to change cards as often. If you use a card this big (regardless of format) take precautions. If you’re shooting a job (photo or video) where you get close to that much data, you don’t want all that data in one place. When time permits, take a few minutes to dump the card onto your computer or portable drive. Use a high speed card reader that can off-put data at 1 GB/minute or faster. The peace of mind will be worth it.