Is The iPad Compatible With SDXC and ExFAT Cards?

After Apple added SDXC and ExFAT compatibility to Mac OS X in 10.6.5, I got to wondering if they had added similar compatibility to the iPad in iOS 4.2.1. Although the hardware reader is probably not SDXC-capable, it wouldn’t have been too hard to add the ExFAT driver from Mac OS X to iOS. Then, the iPad could import from SD cards formatted as ExFAT and USB-connected cameras.

A Little Background on ExFAT and SDXC

For a more-thorough discussion, see An Introduction To exFAT and Introducing SDXC and exFAT in Apple Mac OS X.

As I’ve previously covered in detail, SDXC is the latest digital camera media format and ExFAT is the new filesystem it uses.

SDXC will replace the current SDHC format once cards get past 32 GB: There will be no 48 GB or 64 GB SDHC cards, only SDXC. But SDXC cards remain crazy expensive – this Patriot LX 64 GB SDXC card sells for almost $250! Worse, they aren’t anywhere near as fast as photographers would like, with current offerings poking along at under 20 MB/s just like the SDHC cards they’re supposed to blow away. In short, unless you really need greater-than-32-GB capacity on a single card, there’s no reason to switch yet. But prices will come down and speed will improve in the coming year, and SDXC will likely be common next year at this time.

ExFAT is the new better-than-FAT filesystem selected as the default on SDXC cards. Microsoft created it and added support in Windows 7, and Apple slipped it into some versions of Mac OS X 10.6.4 shipping with new iMacs and Mac Minis this summer. All Mac users get full ExFAT support in Mac OS X 10.6.5, released in November 2010. ExFAT isn’t limited to SDXC, though. Expect to see it on larger flash drives soon, and even portable hard disk drives may use ExFAT rather than NTFS at some point.

SDXC cards still rely on the outdated MBR partitioning scheme, so even though they’re theoretically capable of 64 zettabytes of capacity, real-world cards will top out at “just” 2 TB. SDXC readers and cameras (like my Sony NEX-5) are backwards-compatible, but SDHC hardware can’t access an SDXC card. But USB-connected SDXC readers and cameras should work fine with any computer that has an ExFAT driver.

Testing ExFAT on iPad

Although I don’t have an SDXC card for testing, one can build a reasonable facsimile by formatting an SDHC card with MBR and a single ExFAT partition. I repartitioned a 16 GB SanDisk Ultra II card using Disk Utility in Mac OS X and experimented with it on my iPad with the Apple iPad Camera Connection Kit (MC531ZM/A) SD and USB readers, the NEX-5 camera, the internal SD reader in my late-2009 iMac, as well as an ExpressCard SD reader in my MacBook Pro. The iPad and both Macs were running the latest OS releases as of early December 2010.

Although I haven’t written about it before, I find the iPad Camera Connection Kit useful but far from perfect. I enjoy being able to copy photos to the iPad for big-screen examination and sharing, but the simple import interface uses too-small thumbnails to select the right picture. And it’s way too easy to delete photos from the SD card rather than keep them there for the real (iPhoto, Photoshop, or Aperature) import.

The iPad is SDXC-capable in theory using USB at least. The Camera Connection Kit’s SD card reader is SDHC-compatible, but it’s unclear if it also supports the new SDXC cards. I’m guessing the answer is no, but the timing of its release makes it theoretically possible. The USB connector should allow any card compatible with the connected camera to work, however, including SDXC cards.

Regardless of the physical card format, the iPad must be able to read a connected card’s logical format. In the case of SDXC, this is ExFAT. The bad news is that the iPad (at least as of iOS 4.2.1) does not have an ExFAT driver. Any ExFAT media will appear corrupt to iOS when connected, whether directly accessed using the SD reader or connected using USB.

Insert an ExFAT card and the iPad will pop up the error shown at the top of this post, “Contents Unavailable: The connected storage media may be damaged”. The good news is that the iPad won’t trash the card. The bad news is that it refuses to read the contents.

How To Read SDXC or ExFAT On An iPad: PTP

But there’s another way to read images off a camera’s card. Rather than using the USB “mass storage” (also known as “bulk”) access method, we can access the contents using Picture Transport Protocol (PTP). This simple protocol allows a connected camera to present “objects” like digital images to a connected computer without allowing direct filesystem access.

In short, PTP allows the iPad to access ExFAT, and ought to allow it to interact with SDXC cards! Leaving the card in the camera allows the physical card to be accessed, and PTP allows the iPad to browse and transfer the images.

Here’s how to read an SDXC card on an iPad:

1. Leave the card in the camera
2. In the camera’s settings menu, select “PTP” rather than “Mass Storage” as the USB access method
3. Attach the iPad’s USB “dock dongle” to the camera using a USB cable
4. The iPad will access the images or movies on the card as usual

This same approach will allow computers that lack an ExFAT driver to access SDXC cards as well!

Stephen’s Stance

SDXC is fairly disappointing today, but that won’t likely stop it from wide usage. The performance isn’t there, the pricing is crazy, and not every device is compatible with Microsoft’s proprietary ExFAT filesystem. And what were they thinking when they specified MBR with its 2 TB capacity limit?

It’s not that surprising that Apple hasn’t (yet) added an ExFAT driver to the iPad. This is especially true if the current SD card reader can’t handle SDXC media. It’s nice to know that the iPad can use SDXC cards over USB with the PTP method described above.

Now that Mac OS X includes ExFAT support, I expect Apple to quietly add it to iOS in the future. I’ll keep testing it as releases appear and will report back here then it is added!