The difference between SDHC and SDXC can be confusing. It would be nice if we could just buy whichever one we thought we needed, but there are differences between the two and they aren’t fully compatible or interchangeable with one another. Here’s how to know which to buy, and what other important things you may need to look for.
The difference between SDHC and SDXC is capacity. SDHC tops out at 32 GB, but ExFAT, the technology that lets SDXC go beyond 32 GB, isn’t compatible with all devices or operating systems, so you need to check compatibility before you buy.
The difference between SDHC and SDXC
SDHC and SDXC are both successors to SD cards, the popular digital camera flash memory format. SD stands for “Secure Digital.” SDHC stands for “Secure Digital High Capacity.” SDXC stands for “Secure Digital eXtended Capacity.” In this case, extended is higher than high.
SDHC cards range in size from 2 GB to 32 GB.
If 32 gigs isn’t enough for you, then you need SDXC, which ranges in size from 32 GB all the way up to 2 terabytes.
But the two devices aren’t completely interchangeable. SDHC cards and SDXC cards are formatted differently. SDHC uses the FAT32 filesystem, which was popularized by Windows 98. Yes, it’s an old technology, but well-understood. The problem is that FAT32 can’t scale to capacities higher than 32 GB. That’s why your Windows computer doesn’t use FAT32 anymore. SDXC uses a newer technology called ExFAT. ExFAT can create files larger than 4 GB, so an SDXC card can record video files longer than an hour without breaking them into multiple files.
Checking SDXC compatibility
Not all digital cameras and other devices that use SD-type cards are compatible with ExFAT, and that makes them incompatible with SDXC. Look for the SDXC logo on the device you want to use an SDXC card in. If there’s no logo of any kind, you’ll need to research compatibility. Searching for “SDXC” plus the name of your device in your favorite search engine should get you some answers pretty quickly. If your device was made after 2010, it’s probably compatible, but make sure you check before you spend your money.
You can also get SDHC and SDXC in micro-SD format. The micro versions are called micro SDHC and microSDXC, respectively. The difference is just the physical size, and you can convert micro to full-size using an adapter.
Which is better, SDHC or SDXC?
If your device is compatible with SDXC, SDXC is better. In an incompatible device, SDXC is worthless to you, so in that case, SDHC would be better. If you want to play it safe compatibility-wise and can live with 32 GB of capacity on a card, SDHC is admittedly a safer choice.
But when recording video on a compatible device, there is a definite advantage to using SDXC, since it doesn’t have to split long videos into 4 GB segments. So I’m not telling you to avoid SDXC. I’m just saying to make sure your device will work with it.
SDHC vs SDXC refers only to capacity
The names SDHC or SDXC refer only to capacity. They have no relevance on quality, and negligible relevance on speed. In practice, a less-full device tends to outperform one that’s nearly full, and ExFAT is a newer, better technology than FAT32, so it’s not fair to say two identically rated cards, one SDHC and one SDXC, will perform at exactly the same speed. They probably will at first, but as the smaller card fills up, the larger card is likely to gain a slight performance edge. Whether that edge will be enough for you to actually notice is another question, however.
The speeds of SDHC and SDXC are rated by class. Class is the card’s guaranteed minimum write speed in megabytes per second. A class 2 card can write at least 2 megabytes per second. A class 10 card can write at least 10 megabytes per second. A higher-class card is more expensive, but if your camera is sluggish, a common complaint with older cameras, replacing the card with a faster card may relieve the sluggishness at a lower price than buying a whole new camera.
A card may perform better than its rated speed, it’s just not guaranteed to do so.
Read speeds are usually faster than writes, but write speed is more critical with cameras. If you miss your shot due to lag, a high read speed when you get back home doesn’t exactly make up for it.
What about quality?
It’s best to stick with cards from reputable manufacturers. One safe bet is to buy from the companies who actually make the chips that go into the cards. They get the first pick of the chips before selling them to someone else, so they have an inherent advantage. The companies who make their own chips are Lexar (a division of Micron), Samsung, Sandisk, and Toshiba. I’ve also had success with companies like Kingston, PNY, and Transcend. I recommend avoiding no-name cards when you can, because there’s no way to know what kind of testing they did with the chips before they made the card. You’ll get better, more consistent performance and reliability out of the companies who sell a lot of cards and have a reputation to protect.