If you are a photographer, you are probably familiar with memory cards. They're what our pictures are stored on — removable flash media that we insert into the slot (or slots) on our camera, take pictures, and then (sometimes) remove and insert into a card reader or card slot on our computer.
Almost all of this is obvious to anyone reading this, but where it gets more complicated are all the different types of memory cards that are on the market. Some have very similar names that can easily confuse beginners (eg CompactFlash vs. CFast vs. CFexpress). To complicate matters further, there are many different subclasses of cards within each type.
To make things easier, we've put together this handy guide that will explain all the different types of camera storage media, along with the ones in types.
Digital Security (SD / SDHC / SDXC / SD Express)
Secure Digital (or more commonly “SD”) cards are undoubtedly the most popular type of memory card on the market. Introduced in 1999 by a joint effort between SanDisk, Panasonic, and Toshiba, the SD card was designed to compete with Sony's Memory Stick. Secure Digital was also designed as an alternative to Toshiba's SmartMedia, which in 2001 had 50% market share for digital camera use. By 2005 SD had over 40% of the market, and by 2007 SmartMedia had fallen off the map.
To this day, SD cards are still the most used form of storage for digital cameras. It's cheap, small, and can be very fast. The small size also allows manufacturers to implement dual card slots into very compact bodies. Likewise, it is very common for a camera to feature an SD slot along with another card type, such as CompactFlash or CFexpress.
SDHC vs. SDXC
Most SD cards manufactured today are SDXC — Adorama lists 34 SDHC cards on their site, while SDXC stocks stock at 147 cards. The only difference between them is that SDHC cards are over 32GB, while SDXC (Extended Capacity) cards can store up to 2TB.
UHS Bus Speed
This category is very important. There are two types of SDHC or SDXC cards - UHS-I and UHS-II. UHS-II has a second row of pins and uses low-voltage differential signaling technology, allowing read speeds of up to 312MB/s. UHS-I tops out at 104MB/s. There's also UHS-III, but there's nothing on the market that uses these specs yet (and it doesn't look like anyone ever will).
In short: faster is better, but only if you have a capable camera to take advantage of it. Many mid-to-high-end cameras feature one or even two UHS-II slots, while some feature one UHS-II slot and one UHS-I slot, or even just one UHS-II slot. Some low frequency cameras use UHS-I exclusively.
While you can use a UHS-II card in a UHS-I slot (and vice versa), you will only see the benefits of a UHS-II card when you use it in a UHS-II slot. In other words, UHS-II will play at UHS-I speeds in a UHS-I slot (the same goes for a UHS-I card reader).
Likewise, if your camera has dual card slots, but only one is UHS-II, write speeds (and buffer dumping) will be affected by the slower UHS-I card slot if you choose to save to both cards as a backup.
Unless you're a pure hobbyist or on a tight budget, we highly recommend getting a UHS-II card. It's not significantly more expensive anymore, and you'll be glad you did, even if it's only because transfer times to your computer are reduced.
speed class
Almost any SD card on the market will be labeled Class 10 - there are a few lingering Class 4 cards you can find that are brand new, but for the most part, they are all Class 10. Just look for the little "10" inside the A "C" on the front . This number was used to indicate that the card was capable of at least 10MB/s read and write speeds, while lower classes indicated lower MB/s speeds.
This was most important when memory cards in general were much slower, but these days while you still encounter it on some modern cards, it's pretty useless. The Speed Class has effectively been replaced by either the UHS Speed Class or the Video Speed Class, and it would be better to limit the card's capability.
UHS Speed Class
This is the more recent version of Speed Class, as virtually all existing SD cards fit in one of two UHS Speed Classes - either U1 or U3. Denoted by either the number 1 or the number 3 inside the letter 'U' - usually found somewhere near the speed class. Most cards will be U3, which indicates a minimum write speed of 30MB/s.
Video speed class
While this seems to be more important for video than photography (and it is, to an extent), it is the best indicator of the card's write speed performance, which can be important for photographers who shoot a lot of bursts and want to clear their buffer as quickly as possible. The faster write speed means the camera's buffer can dump files to the memory card in less time, freeing up space more quickly to continue shooting.
There are three classifications here: V30, V60 and V90. The meanings are simple: the V30 is capable of a minimum of 30MB/s, the V60 is capable of at least 60MB/s, and the fastest, the V90, has a minimum write speed of 90MB/s.
For most photographers, we'd just recommend the V60 cards - they're a great balance of speed and affordability. If you shoot 4K (or higher) video, you may want to invest in V90 cards, depending on your camera. Basic 8-bit footage will write easily to V60 cards (or often even V30), and most 10-bit 4K images will be fine on V60 cards, but high-quality footage like ProRes RAW or regular RAW may need at least a V90.
Most camera manufacturers will indicate the speed of memory cards required for a particular resolution and bit rate in the manual or on their website. High-end cameras that now do 8K internally - the Canon R5, Sony Alpha 1 and Nikon Z9 - use a completely different memory card format called CFexpress, either Type A (Sony) or CFexpress Type B (Canon and Nikon) because even V90 cards aren't enough. for this level of data.
Shoot for the UHS-II V60 card if you want to balance quality, speed and affordability - it's more than enough for photography as well as most video. The jump from the V60 to the V90 will hit you in the cost of the upgrade, so there's no reason to do it if you can't take advantage of it.
SD Express cards
Avoid these at all costs. There are no cameras that support the format and none of the experts think any of the experts will. I repeat: no camera on the market in any class supports the SD Express format. Without this support, you'll get worse performance while paying a lot more than SD UHS-II cards.
MicroSD (and MicroSDHC / MicroSDXC)
MicroSD are pretty much what they sound like: smaller versions of SD cards. These cards are commonly used in smartphones, action cameras, some smaller cameras such as the Sony RX0 II, and some drones such as the DJI Mavic 3 and DJI Mini 2.
All of the same specifications for SD cards apply to MicroSD cards, with the same nomenclature. Both UHS-I and UHS-II microSD cards are available, ranging from the V30 to the V90 — although only Delkin Devices and Kingston produce V90 cards, so the selection is much thinner than SD for high-speed options.
MicroSD cards can also be used in the regular SD card slot with the MicroSD to SD Adapter. If you purchase a UHS-II MicroSD card, make sure the adapter is also UHS-II. Many MicroSD cards are sold along with compatible adapters.
Adapters are also the easiest way to transfer data to your computer, although many external multi-slot card readers come with MicroSD slots as well.
Compact Flash (CF)
The CompactFlash (or simply "CF") card is one of the oldest and most popular memory cards of all time. First manufactured in 1994 by SanDisk, CF cards offered an excellent price-to-capacity ratio as well as larger available capacities compared to other formats on the market. CF cards were widely adopted in the first DSLRs and continued to be used until about 2016 - the Nikon D810 and D4 flagship cameras had CF slots, as did the Canon 1DX Mark II and 1D C.
With the release of the Nikon D5 and D500 in 2016, Nikon switched to the XQD (with subsequent firmware updates for CFexpress compatibility), while Canon similarly adopted CFexpress Type B with the 1DX Mark III.
CompactFlash, which uses the Parallel ATA interface, has been replaced by a new format based on the faster Serial ATA interface - the CFast Card. As such, CF is no longer used in new products, but a lot of cameras on the used market use the format, and you can still buy brand new CF cards. All current CF cards are UDMA 7 compliant and generally boast about the same read and write speeds (around 120 to 160MB/s). The read speed will be printed on the card itself and you can refer to the product specifications for the maximum write speed.
If you have an older digital camera, be sure to check the card's maximum capacity - I've had a number of cameras that are 1GB or even 512 or 256MB.
CFast 2.0
CompactFlash's successor, now based on the Serial ATA (SATA) interface, first hit the market in 2009, though it will take several years for the imaging industry to fully embrace the format.
CFast 2.0, while similar in shape and size, is not backward compatible with CompactFlash. Nor is it super relevant for photographers or even videographers who use modern still photo/camcorder hybrids. The format is usually reserved for dedicated cinema cameras - Blackmagic, some RED models, etc. - and even then they are being phased out and replaced with either dedicated HDDs or CFexpress. Don't worry about this unless you use such cameras.
If you do, everything is pretty straightforward: a CFast 2.0 card is a CFast 2.0 card. Just look at the read/write speeds indicated on the cards to get an idea of what each is capable of.
XQD
First announced in 2010 by SanDisk, Sony, and Nikon, the XQD is a flash memory card that uses the PCI Express interface. XQD version 2.0, announced in 2012, has moved to the PCI Express 3.0 interface.
XQD has been widely adopted by Sony in its broadcast camcorders, primarily due to the high transfer speeds offered by XQD. In the world of photography, Nikon has been the biggest supporter of the format – the Nikon D4, Nikon D4s, Nikon D5, Nikon D6, Nikon D850, Nikon D500, Nikon Z6, and Z7 all feature one or more XQD card slots. The Phase One also uses the format in the XF IQ4 camera system.
Unlike CFast 2.0, XQD is in many cases compatible with its successor: CFexpress Type B. Nikon D5, D500, D850, Z6, and Z7 have received firmware updates to support the use of CFexpress Type B cards in addition to XQD.
You can still buy new XQD cards, though unless you have Nikon D4/D4s that only support XQD, you're better off using CFexpress Type B provided you update your camera's firmware - CFexpress Type B tends to be a bit cheaper due to to wider adoption and more importantly more future-proof.
What brands of memory cards should you buy?
With any of these types of memory cards, our suggestions for the best brands are SanDisk, Lexar, Angelbird, Sony, ProGrade Digital, Delkin Devices, Exascend, and Wise.
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