A guide for SD card classes

Selecting the right SD card helps to save cost and improve your devices’ performance. Especially when using a camera or camcorder to take videos or continuous shooting, a good SD card really matters. As SD card has been an essential storage for your digital devices by storing data, it is a necessary to know the standard of SD card classes.

How is the type of SD card classes?

Class is a guidance of speed for memory cards launched by SD Association. To distinguish SD cards among different writing or reading speed, there are various types linking to the speed ratings.

Speed Class	UHS Speed Class	Video Speed Class
“Speed Class“ Mark C10	“UHS Speed Class” Mark u3	“Video Speed Class” Mark v90

1. Speed Class – this is an older generation of speed family, the market used it in last decades. Normally number with a circular “C” symbol is telling minimum write speed.
   • Class 2 (C2): The minimum write speed is 2MB/s. This is the slowest version for this type, most SD cards in low capacity offers this speed.
   • Class 4 (C4): 4MB/s by write
   • Class 6 (C6): minimum write speed of 6MB/S
   • Class 10 (C10): minimum write speed of 10MB/S. C10 is the main demands for present devices, users prefer fast reaction.
2. UHS Speed class – It is an updated version of speed; the full name is Ultra-high speed. There is “U” symbol together with number to tell different types. Two main ratings within the UHS speed class are as follows.
   • UHS-1 (U1): The minimum write speed reaches 10MB/s. Comparing with class 10, many dash cams and DSLR cameras prefers U1 type. As the UHS bus interface provides a sustained write performance, it is perfect for 1080P or 4K video recording.
   • UHS-3 (U3): minimum write speed at 30MB/s. High-end cameras or drones always take a U3 rated SD card. Regardless of a high write speed, its read can hit up to 104MB/s
3. Video Speed class – This is the latest feature to support higher video resolution. They are displaying in “V” symbol.
   • V30: minimum write speed at 30MB/s
   • V60: lowest writing speed of 60MB/s
   • V90: minimum write speed at 90MB/s

The importance of SD card classes

When purchasing SD cards, users firstly will check the speed, and then it is the capacity. With a faster writing or reading, a camera can shoot a larger number of photos per minute. Even you purchase a 128GB or 512GB SD card, the recoding time is slow if you ignore the speed. In addition, the parameter of devices must be checked prior to order SD card. As you need to confirm the speed range of your equipment, it will make sure a good performance.

1. High SD speed classes enhance your devices’ performance
   • Action photography normally shoots photo in RAW format, each image displays in 41 MP and occupies over 25MB. To avoid any delays on photo loading, U1 and U3 class are the best option.
2. Speed version tells the cost
   • Normally we can know the cost range of SD card by capacity and speed. However, high capacity not always deliver high cost if the speed is slow. For example, one 128GB SD card class 10 is much cheaper than U1 or U3 version. Therefore, the lowest price is hard to guarantee high speed.
3. Speed backward compatibility
   • Bulk memory cards are able to be backward compatible within its generation. For instance, you can use one SDHC card in SD version slot. The only difference is that the device will work at the slowest speed of memory card. Thus, if you use one U3 SD card in U1 slot, the fastest speed will be same as U1 standard.

SD speed classes for host device

In order to bring users convenience, devices suppliers will mark class symbol on their hosts. It indicates a minimum speed request; the equipment cannot work properly if you use lower speed.

1. Host device requests for Class 4 SD card: You can use SD speed at Class 4, 6 and class 10
2. Host device asks for UHS-1 SDHC Card: It means it supports UHS-1 or UHS-3 memory cards.

Device with Video speed class has the same rule request as above. Therefore, it is wiser to check these details prior to order any bulk SD cards.

Benefits from fast SD Cards

As if the devices can support high speed type, SD cards in fast speed offer a good performance. Let’s research into these benefits from different devices.

1. Game console such as Nintendo Switch: A good game experience is guaranteed if you use a faster card, which is helpful for games loading.
2. Cameras: Photographers prefer continuous shooting modes. As speedy cards can catch up with an efficient storing, it means numbers of photos can be shoot at once. Especially, when you use camera to take photo in 4K or 8K, a U3 SD or CFexpress card can record extreme high-resolution images.
3. 3D printer and Raspberry Pi: You can save lots of time if you get fast SD card using there.

Notes on purchasing SD memory cards

Obviously, the cost is more if you choose a large capacity and high speed card. However, the purchase instruction should follow up the requests of devices. For example, your GPS device tells class 4 workable for data recording, then class 4 SD card is good and cheap enough for supporting its performance. Likewise, if you are engaging in photography business, a large amount of data transfer is a must for daily job. In this way, you ‘d better consider SD cards in higher speed and larger capacity.

Conclusion

SD speed rating is a key parameter for measuring speed of writing and reading, normally it is expressed as megabytes per second. Class speed on cards is telling minimum speed of recording, as if users know well of these specificat