SDXC > SDHC ? Not necessarily. - AVS Forum
Camcorders > SDXC > SDHC ? Not necessarily.
Ungermann's Avatar Ungermann 01:53 PM 03-22-2013
If your camcorder supports SDXC, what cards you should buy: SDHC or SDXC? The answer may seem obvious: of course SDXC, because they are newer and as such better. But what exactly is better about them?

* Old school SD cards (SD 1.0, SDSC) use FAT file system. It is old, free, reasonably fast. Capacity is limited to 2 GB I believe.
* SDHC cards use FAT32, it is free, reasonably fast, capacity is limited to 2TB (not bad), but max file size is limited to only 4GB (this is why AVCHD files are 4GB max (on Pana) or even 2 GB (on Canon, supposedly because of twice smaller cluster size).
* SDXC cards use exFAT, it is not free, therefore either camcorder manufacturers or card manufacturers or both, I haven't figured that out, have to pay royalties to Microsoft for usage of this patented file system. And because it is patented, you cannot get it for free in Linux distros. Capacity is limited to... some really huge number :-). The allocation table is more complex, hence it may take more time to write to the card (this is my own theory).

Then comes speed rating. It is not directly related to card being SDHC or SDHC. It is possible to have an SDHC card with U-rating (like UHS-I), it is also totally possible to have an SDXC card without U-rating rating.

And it may turn out that older SDHC cards are faster than SDXC. This is not important when you shoot, but it may take you three to five times longer to dump content of a slow SDXC card than of a fast U-rated SDHC card, provided that you have fast USB3 reader.

Here are some tests to prove the point.

This is a test of the ADATA Premier Pro 32GB SDHC UHS-1 Memory Card. The card is rated at 95MB/s read and 45MB/s write. Reader used: Transcend TS-RDF8K (USB 3.0).

This is a test using the same reader. Only SDXC cards in the test. UHS-I rated Patriot LX is 60% faster than a Class 10 card. Still, the 30 MB/s SanDisk card (SanDisk seem to have deep disdain to C- and U- ratings) is even faster, still "only" at 40 MB/s.

Finally, a Polish test using the same reader. They used a fast SDHC card (they say it is rated to 80 MB/s, sadly they did not provide the model or class) and a slower SDXC card (again, no model or rating, but as you can see, SDXC cards can be slow!) The difference is 3:1 or read and about 2.5 : 1 on write. They used 11 large files, total about 15GB.


* Buy SDXC cards only if you really-really-really need more than 32 GB of storage per card. Do you? I don't. Most of my cards are still 4 GB, they dump nicely to a recordable DVD, although I bought a couple of 16 GB recently.

* If you shoot a lot of videos or photos and you cannot wait for the files to copy from card to your computer, consider buying a USB3 reader (you need support for USB3 on the computer) and look for U-rated cards. AFAIK, the only class available for now is UHS-I. As these tests show, these cards are at least twice faster for dumping files onto computer than Class 10 cards.

* If you buy SDXC cards make sure they are U-rated. But you can see from the tests, that even UHS-I SDXC cards are about twice slower than UHS-I SDHC cards. I think this is where the exFAT overhead shows its ugly head. Or tail. Or the whole ugly body.

Anyway, as for me personally, I will be buying SDHC cards only for forseeble future. I need to check with my cameras (I have multiple). The Canon HF100 won't take Class 10 cards without firmware update, and I don't know whether it will ever take UHS-I. The 2008 HDC-SD9 has no problems with Class 10 cards, I need to try it with a UHS-I card. I sold the HMC40... Oh, the Nikon D3200, need to check it with a UHS-I card as well.

Need to get myself a fast reader too.

STR3T's Avatar STR3T 02:16 PM 03-22-2013
Good stuff, Ungermann.

Yeah, I'd only buy an SDXC if I needed really high capacity...64GB+.

Even w/ an extra, full sized battery for the TM900, I run out of juice before space with a 1 x 32GB and 2 x 16GB cards at full resolution. Rarely need the other cards at a 2-3 day soccer tourney, taking in 3-6 1hr games.
jogiba's Avatar jogiba 08:51 AM 03-23-2013
I use a 64GB SanDisk Ultra SDXC UHS-1 in my Sony NEX-VG900 but also have four low cost Sony 16GB SDHC Memory Card Class 10 UHS-I cards that sell for $18.95 for a two pack w/FS at B&H.

bsprague's Avatar bsprague 10:14 AM 03-23-2013
Originally Posted by jogiba View Post

I use a 64GB SanDisk Ultra SDXC UHS-1 in my Sony NEX-VG900 but also have four low cost Sony 16GB SDHC Memory Card Class 10 UHS-I cards that sell for $18.95 for a two pack w/FS at B&H.

Do you have a link to the $18.95 deal? I can't find anything close.


mvpers's Avatar mvpers 11:31 AM 03-23-2013
bsprague's Avatar bsprague 03:13 PM 03-23-2013

Buy now! The fine print says it is good until the end of today.
Ungermann's Avatar Ungermann 03:58 PM 04-01-2013
More charts.

This is a chart from Guru3D. They used USB3 reader, did not specify which one.


This is a chart from Bright Side of News, you can see that a UHS-I SDHC card is faster than an SDXC card. They used a Kingston USB 3.0 external media reader.


This is a speed test of the SanDisk Extreme Pro microSDHC UHS-I 16GB memory card in the Kingston MobileLite G3 reader from Legit Reviews.

STR3T's Avatar STR3T 04:39 PM 04-01-2013
That Patriot comparison from Bright Side of News is odd...thought the rule of thumb was (HDD as well as SDD's) the larger capacity disks were usually faster than smaller capacity? In general, I guess this is due to improving technologies which naturally occurs as capacity grows. Not always true, but that's a bit jump from 32GB SDHC to 128GB SDXC.

Glad I didn't bet anybody on that result!
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