Memory cards might be the most important part of your kit, used in either photo cameras, video cameras, smartphones or other devices. Their performance is defined by various ratings, which can be confusing. This article guides you through these ratings, helping you choose the right memory for the job.
With CF and CFE Cards there isn't that much choice. I recommend buying a card from a brand you trust. With CFE you want to check your camera manual for recommendations. Everything below is for SDCard and microSD.
In theory it indicates the maximum bus speed of a card, affecting data transfer rates. However it depends on what your device can support. Although these interface levels are downward compatible, the price difference is huge. Getting UHS-II when you really only need UHS-I is a waste of money.
This is the official spec: UHS-I: Officially has a max. speed of 104 MB/s (modern cards can do 200MB/s anyways) UHS-II: Higher maximum bus speed of 312 MB/s, thanks to an additional row of pins. UHS-III: Newest standard with a maximum bus speed of up to 624 MB/s.
UHS (Ultra High Speed) Speed Class is found on UHS-equipped devices, offering faster writing speeds. I don't recommend cards that do not have U3 printed on them.
U1: Minimum writing speed of 10 MB/s. Good for full HD video recording. U3: Minimum writing speed of 30 MB/s. Supports 4K video recording.
Introduced to support higher video resolutions and recording features, Video Speed Class is denoted by a "V" followed by a number. In most cases I recommend V30.
V6, V10: Similar to Class 6 and Class 10, respectively - do not choose those. V30: Minimum writing speed of 30 MB/s. Suitable for 4K video. V60: Minimum writing speed of 60 MB/s. Can handle 8K video with a high frame rate. V90: Minimum writing speed of 90 MB/s. Designed for 8K video and beyond. UHS Bus Interface
Depending on the size you might find one of the following markings. If you have a older camera you want to check the manual for which card "type" they support. This is how
SD (Secure Digital): Up to 2GB of storage. SDHC (Secure Digital High Capacity): Between 2GB and 32GB. SDXC (Secure Digital eXtended Capacity): Between 32GB and 2TB. SDUC (Secure Digital Ultra Capacity): From 2TB up to 128TB. Choosing the Right Memory Card When selecting a memory card, consider your device's compatibility and your specific needs, such as video resolution, speed requirements, and storage capacity. Higher ratings typically mean better performance but also a higher price. Balancing your requirements with your budget will help you make the best choice.
Aimed at running applications directly from the memory card, the Application Performance Class guarantees minimum levels of random read and write speeds measured in Input/Output operations Per Second (IOPS). Cards without this rating might have a fast speed, but only when reading a large file. Applications often have thousands of small files. That is why this rating exists. For a raspberry pi or smartphone you might want A2.
A1: Minimum 1500 read IOPS and 500 write IOPS. Ensures smooth app performance. A2: Higher performance with 4000 read IOPS and 2000 write IOPS, reducing app loading times.
The Speed Class rating indicates the minimum writing speed of a memory card in megabytes per second (MB/s). It is not very relevant anymore. Simply do not buy a card that is not C10.
Class 2 (C2): 2 MB/s. Suitable for standard definition video recording. Class 4 (C4): 4 MB/s. Can handle HD video recording. Class 6 (C6): 6 MB/s. Supports HD and some full HD video recording. Class 10 (C10): 10 MB/s. Designed for full HD video recording and consecutive recording of HD stills.