Memory Cards

Memory Cards

Memory cards are removable storage for cameras, dash cams, drones, audio recorders, security cameras, tablets and handheld devices. NXP stocks SD and microSD cards from SanDisk, Verbatim and ADATA in 32GB to 256GB, alongside USB 3.0 card readers from StarTech.

SD or microSD

SD is the full-size card, roughly the size of a postage stamp. It is what most cameras, camcorders and audio recorders use, and it carries a physical write-protect switch on the side.

microSD is much smaller and is used in phones, tablets, dash cams, drones, action cameras, security cameras and single-board computers.

Many microSD cards — including the ADATA Premier in this range — ship with an SD adapter, so one card serves both slots. If you are buying for mixed devices, a microSD with adapter is the more flexible purchase. It does not work the other way round: a full-size SD card cannot be made to fit a microSD slot.

SDHC or SDXC: a capacity distinction, not a quality one

These are not grades of quality. They are capacity tiers:

• SDHC — 4GB to 32GB. Formatted FAT32 by default.
• SDXC — 64GB to 2TB. Formatted exFAT by default.

The practical consequence is compatibility. An older device that only supports SDHC will not read an SDXC card, however you format it. Check the device's maximum supported capacity before buying a large card — this is far and away the most common reason a new memory card "doesn't work". The same distinction applies to microSDHC and microSDXC.

Speed ratings, decoded

Card packaging carries several overlapping rating systems. Here is what each one actually tells you.

• Class 10 — minimum 10MB/s sustained write. The baseline for HD video, and effectively standard now.
• UHS-I — the bus interface, which raises the ceiling on transfer speed. Almost all current cards are UHS-I. UHS-II exists and is faster, at a price.
• U1 / U3 — minimum sustained write of 10MB/s and 30MB/s respectively. U3 is what 4K video needs.
• V10 / V30 / V60 / V90 — the video speed class, and the most useful figure if you are recording video: the number is the guaranteed minimum sustained write in MB/s. The ADATA card here is V10.
• A1 / A2 — application performance class, which measures random read and write rather than sustained throughput. It only matters if you will run apps from the card, as on a tablet or a single-board computer.

The large MB/s figure on the front of the pack is the read speed — the fastest number, and the least relevant one for recording. What matters for video and burst photography is the minimum sustained write speed, which is exactly what the U and V ratings describe.

Which card for which job

• Photos on a compact or DSLR — 32GB or 64GB, Class 10 / UHS-I. Several smaller cards are safer than one large one: if a card fails you lose part of the shoot rather than all of it.
• 4K video — U3 or V30 as a minimum. A slower card will drop frames or stop recording mid-clip.
• Dash cams and security cameras — these write continuously and overwrite constantly, which is punishing on a card. Use at least 64GB to spread the write cycles, and check the camera's supported capacity.
• Tablets and handheld devices — 128GB or 256GB microSD, A1 class if you will run apps from it.
• Audio recorders — 32GB is generally ample. Audio files are small next to video.

Card readers

Most laptops no longer have an SD slot, so a USB 3.0 card reader is the practical answer. The USB 3.0 part matters: transferring a full 128GB card over USB 2.0 is a genuinely long wait. The CFast reader in this range is for professional video and high-end photography workflows using CFast media. If your laptop is short on ports altogether, a USB hub is worth pairing with the reader.

Looking after them

Cards fail, usually without warning. Copy files off promptly rather than treating the card as long-term storage, format in the camera rather than on a computer, and replace cards in continuous-write applications such as dash cams on a schedule rather than waiting for a failure.

For storage that stays put, USB flash drives suit file transfer and external hard drives suit backup and archive.

Frequently asked questions

What is the difference between SDHC and SDXC?

Capacity, not quality. SDHC covers 4GB to 32GB and is formatted FAT32; SDXC covers 64GB to 2TB and is formatted exFAT. An older device that only supports SDHC will not read an SDXC card, so check the device's maximum supported capacity before buying a large card.

What speed memory card do I need for 4K video?

U3 or V30 as a minimum, which means a guaranteed sustained write of 30MB/s. A slower card will drop frames or stop recording mid-clip. Ignore the large MB/s figure on the front of the pack — that is the read speed, not the sustained write.

Can I use a microSD card in an SD slot?

Yes, with an SD adapter, and many microSD cards include one — the ADATA card in this range does. It does not work in reverse: a full-size SD card cannot fit a microSD slot.

What size memory card should I buy for a camera?

32GB or 64GB suits most photography, and using several smaller cards rather than one large one limits how much you lose if a card fails. For 4K video, go larger and prioritise the sustained write speed rating over the capacity.

Why will my new memory card not work in my camera?

Most often the card exceeds the capacity standard the device supports — an SDHC-only camera cannot read an SDXC card. Check the maximum supported capacity in the manual, then format the card in the device itself rather than on a computer.

Do I need a card reader, or can I plug the camera in?

Either works, but a USB 3.0 card reader is usually faster and it saves running the camera's battery down during a long transfer. It also lets you offload one card while continuing to shoot on another.