Published: August 30, 2019 | Last Updated: August 29, 2024
Every camera manufacturer seems to have adopted a separate digital media standard. The result is many storage media types, ranging from various SD cards and CFast cards to external SSDs. Each has different sizes, write speeds, and read speeds.
To add to the confusion, some cameras even accept different types of cards (so the first thing to do is always to check compatibility). You can also record to an external recorder, which uses a different card or SSD than the one used in the camera.
In this article, I’ll dispel the confusing world of memory cards, walk you through the many different formats, and explain when to use what.
Size Capacity
As our capacity to record 4K, 6K, 8K, and beyond has increased, the capacity of gigabytes our memory cards can hold has needed to keep pace with the increase in resolution and definition.
Higher frame rates, color bit depths, and heavier codecs have all contributed to the need for bigger memory cards.
The underlying technology of the card limits size capacity, and you’ll see as we go through the various memory cards how a card’s file formatting system can determine how much space it can hold.
In other words, don’t buy too few or too small of memory card storage capacity-wise because you’ll need all the storage you can get – and will likely run out of it sooner than you may think.
One thing to note: just because the card says it can hold up to 128GB of data doesn’t mean you can record up to the full 128 GB. Some internal card files take up space, but the exact amount of “true space” will vary from brand to brand. You can research the brand and card you want to get specifically to find out the “true size,” as that information is case-by-case.
Speed Capacity
The type of video codec you are trying to shoot will determine what type of card you may need.
To determine which card goes with which codec, you must assess the memory card’s write speed and, in some cases, read speed. These two factors are essential for your card’s overall performance and compatibility.
Read Speed
Read speed refers to the speed at which you can watch back your video files on your memory card.
If a memory card has a high read speed, the pace at which you can open and review files will be very efficient with very little lag time, as opposed to a slower read time, where it might take more time to load and access clips.
Just like how the space capacity listed on a card is not the true amount of space on that card, a card’s read speed, as listed, is often not the true read speed of a card.
For example, if your memory card says it has a read speed rate of 150 MB/s, that is the maximum speed – not its average speed.
A card’s read speed largely depends on the device you use to access it. For example, if you have an older camera, that can slow down an otherwise fast read speed on a newer memory card.
If you are accessing files on a fast USB card reader, no problem, but an older one connected to a fast computer can still slow down your process.
Usually, when it comes to card readers, the memory card brand will have a recommended card reader to use to get the highest read speeds out of your card.
UHS-I vs UHS-II
Smaller memory cards usually have a 25MB/s read speed, but there is a class known as the Ultra-High-Speed (UHS) classification, which refers to any card with a max read speed higher than 25 MB/s.
The UHS-I cards go up to 104 MB/s, while UHS-II cards go up to 312 MB/s.
Read speed is also significant when transferring video files from your memory card to your computer. The faster the read speed, the quicker the transfer speed should be, which is why you want the best card reader possible for your card.
Write Speed
Write speed refers to the speed at which a card records video data.
Write speeds are referred to by their minimum speed, which is the slowest your camera can write data to the memory card without interrupting the capture of the footage.
This is important because certain capture codecs require a minimum speed to record footage smoothly, which we’ll get into later.
Like read speeds, write speeds are also classified by their UHS type. For example, UHS I cards have a minimum write speed of 10 MB/s, and UHS II cards have a minimum write speed of up to 30 MB/s.
Another newer classification of write speed is the Video Speed Classification, which goes from 10 MB/s at V10 up to 90 MB/s at V90.
Now, depending on the codec you are shooting on, you must have a specific write speed classification. For example, if you want to record 4K footage at 400 Mbps with the Panasonic codec All-I on a GH5 or Eva-1, you must have a V90 at minimum.
For most 4K shooting, you will need a class 6 write speed, meaning the card has a minimum write speed of 6 MB/s. Again, that depends on the codec and camera you are using. V90 write speed cards, meanwhile, can shoot up to 8K footage.
Testing the True Speed of a Memory Card
You can run tests to determine how closely a memory card’s read and write speeds match those labeled by the manufacturer.
You can use the AJA System Test, which is free for Mac and PC and turns the data from your cards’ read and write speeds over time into a graph.
Also, the Black Magic Disk Speed Test is great for testing your card’s read and write speeds while calculating whether those speeds will work with specific video codecs.
Remember to acquire the right high-speed card readers for whatever memory card you get to ensure the highest transfer speed from your card to your hard drive or computer.
Consider the cost per GB
Even though SSDs are often more expensive than memory cards – the cost per GB is much lower when you factor in the read and write speed.
Take, for instance, the popular Samsung T5 Portable SSD. You get 500 GB of storage and transfer speeds of up to 540 MB/s, enough to record RAW footage from popular cameras such as the BMPCC 4K, BMPCC 6K, and Panasonic S1H.
Even though you can get SD cards with the same amount of storage for a similar price, you won’t get near those read-and-write speeds.
Another benefit of recording to an external recorder with an SSD is that some cameras can record to both external SSDs and internal cards at the same time. This can be used for creating proxies or having a lower-quality backup recorded onto, e.g., an SD card in the camera.
To put these prices in perspective, the capacity to condense space has increased exponentially over the last decade.
However, recording to external SSDs can result in a bad transfer cable and lost data. These dangers are mostly avoided using cameras—such as RED—that record to SSDs via a cartridge/mag directly inserted into the camera.
The Different Card Types
Now that we’ve covered the basics let’s explain each type of card in more detail.
SD Cards
SD cards, or Secure Digital cards, are the go-to memory cards for DSLRs, computers, audio players, and smartphones. There are three types of SD cards: standard SD cards, SDHC cards, and SDXC cards.
SDHC cards, short for Secure Digital High Capacity, are SD cards that can hold 4 to 32 gigabytes of data. These are the standard SD cards you probably used when shooting video on your DSLR in the early 2000s.
SDXC cards, which stand for Secure Digital Extended Capacity, can hold over 64 gigabytes and beyond. These SD cards are usually used for shooting 4K footage with higher-end cameras.
Fat file management system
The FAT file management system is the biggest difference between SDHC and SDXC cards.
SDHC runs on FAT 32, which allows up to 32GB of storage, and SDXC cards run on exFAT, reaching up to two terabytes. (Remember that cards formatted with FAT 32 are limited to individual file sizes of 4GB per file.)
Also, SDXC cards don’t work with all cameras, especially older ones, so you must research before grabbing one.
MicroSD Cards
MicroSD cards function similarly to traditional SD cards but are about five times smaller than your typical SD card. Because of their size, these cards are ideal when shooting on a smartphone, shooting for long hours, taking real-time footage with a GoPro, or shooting wide-sweeping landscapes with a drone.
MicroSD also comes in microSDHC or microSDXC varieties like traditional SD cards, which helps when shooting with smaller cameras like a GoPro or drone camera.
When uploading your footage, you will need a card adapter that transforms the microSD to an SD card in physical size to work with microSD on devices that aren’t built to support them.
CompactFlash Cards
Moving on from SD cards, we have CompactFlash cards, which were invented for higher-end DSLR cameras. However, with the advent of SDHC and SDXC cards, CompactFlash cards are now an optional choice for cameras that support both SD and CompactFlash formats.
Similar to SD cards, there are two main types of CompactFlash cards: Type I and Type II. The main difference between the two is speed.
The only difference between the two types is the actual physical thickness of the cards.
A CF Type I card is 3.3mm and can only fit into CF Type I slots on a camera.
A CF Type II card is 5mm thick and can similarly only fit into CF Type II camera slots.
CompactFlash cards have a maximum write speed of 167 MB/s; the best ones stay between 60 MB/s and 150 MB/s.
CompactFlash cards can be formatted to exFAT or FAT32, which allows them to be used on Windows or Mac computers.
CFast Cards
CFast cards are among the fastest memory card types available, which makes them ideal for the highest-end DSLR cameras and the memory card of choice for cinema cameras.
They are similar in look and feel to traditional CompactFlash cards but are more powerful in speed.
While the maximum write speed of a typical CompactFlash card caps out at 167 MB/s, CFast cards have been proven to write up to 600 MB/s, though they usually average more like 430 MB/s write speeds.
XQD Cards
XQD cards were initially meant to replace the compact flash card but have become more common in Sony and Nikon DSLR cameras.
It’s worth noting that XQD cards transfer data using PCI Express, which enables write speeds of up to 400 MB/s (megabytes) and storage capacity over 2TB.
However, support for this card type has been discontinued in favor of the CFexpress format cards, which will be released later this year.
CFexpress Cards
CFexpress cards were announced as the next generation of XQD cards when the XQD cards were discontinued in 2018 by owner company Lexar.
CFexpress uses PCIe 3.0 as an interface with up to 8 lanes, each supporting 1 GB/s of data. It was created to be compatible with PCIe and NVMe data transfer standards.
It is one of the fastest cards on the market, with top read speeds of 1,700 MB/s and minimum write speeds of 1,480 MB/s.
These cards are planned to come in three sizes, like SD cards: SD, SDHC, and SDXC. CFexpress cards will be Type A, B, or C sizes.
Solid State Drives
You may also use solid-state drives or SSD memory cards when working with larger cinema cameras.
The big cinema cameras from RED and ALEXA have SSD memory cards that they have created and branded specifically to run on their cameras, like so:
RED Mini-Mag
The RED-branded SSD memory card format, Mini-Mag, is used in popular RED cameras like the RED Scarlet and RED Epic 8K.
Because they are their beast, they also come with the RED Mini-Mag Station adapter to transfer data from your card to your hard drive.
The nice part is that it can transfer data at a top transfer speed of around 300 MB/s since it’s an SSD. Higher-capacity cards typically have faster internals, allowing better compression when using the R3D RAW codec.
SxS Cards
SxS cards are SSD cards created by Sony that work for Sony FS5 and FS55 cameras and third parties like the ARRI Alexa cameras.
SxS cards connect through a connector port called the PCI ExpressCard slot, which is used to connect laptops and all kinds of devices, like FireWire connections, Ethernet ports, externally enclosed graphics cards, and, in the case of SxS cards, extra memory drives.
SxS cards are high-speed, with average transfer speeds of around 1.3 Gb/s (1,300 Mb/s) but with a potential ceiling of up to 8 – 10 Gb/s (which would be around 1,250 MB/s at 10 Gbps) in the newly announced SxS Pro X cards.
To put that in perspective, when we’re talking about Mb/s, that is megabits, so the 10 Gigabit potential of the SxS Pro X cards means you could have theoretical write speeds of 1,200 megabytes. That’s… A LOT of data is written per second!
P2 Cards
P2 cards are Panasonic’s answer to Sony’s SxS cards. Like the Red Mags, they are used only for Panasonic cameras, such as the signature Panasonic Varicam line of cinema cameras.
Like SD cards, P2 cards come in multiple variations, including the standard P2 and microP2 cards, similar to SDXC and expressP2 cards.
While P2 cards max out at 1.2 Gb/s (or 1,200 Mb/s), the new expressP2 cards have a potential ceiling of up to 10 Gb/s. (again, around 1,250 MB/s).
Summing Up
Knowing which memory card is best depends on your camera, the content you are shooting, and the codec you will be shooting on. When selecting the best memory card for your camera, consider the footage’s video resolution and the intended frame rate.
For example, SD cards are the standard memory when shooting with DSLR or similar video camera types. Still, if you are shooting on a camera like a Black Magic URSA Mini or a Canon C200 MK II, you will want to go with an XQD or CFast card.
Meanwhile, microSD cards are better for action cameras and drones when shooting more action-oriented videography.
While you can use microSD cards with adapters, and often, you won’t have problems doing so, some have reported troubles with the connection between the card and the adapter, so an SD card might be ideal.
Also, as mentioned earlier in the article, you should factor in the cost per Gigabyte.
Well, if I was not confused before, I am certainly overwhelmed now. However, it is nice to have so comprehensive a work up on one page.