How To Choose An SD card

How To Choose An SD card

Today it is common to find cameras of various formats, camcorders, smartphones and drones capable of recording video in 4K, an ambitious resolution in data transfer speed requirements and storage. If you’re looking for an SD card for a device that captures 4K video, here’s what you need to know.


Which SD Card to Buy to Capture 4K Video

Which SD Card to Buy to Capture 4K Video

SD cards are a storage system that is very popular for their features. It is a versatile memory, easy to use, durable, backward compatible, compact, with large storage space and relatively affordable.

Although for simplicity, in popular language, we use the term “SD cards” to coexist various formats, types, and classifications. 

The microSD is the most common format today for its versatility because it allows us to insert them directly into smartphones or certain models of compact cameras or use them using an adapter in devices with an SD slot. Before you buy a card model, check its dimensions and whether it includes an adapter.


Capacity, a matter of budget

As for the type of card, we essentially find three: SD, SDHC and SDXC, something that you can check with the naked eye on the card’s surface.

Considering the volume of 4K recording, we will have to opt for an SDXC card; what capacity to choose?

It will depend on what our device allows and our budget, with 128 GB being a good starting point.


By speed: the minimum UHS-I U1

The next thing will be to know the card’s speed, something that the manufacturer informs us through the Class or Speed Class, a classification prepared by the SD Association. This figure, which is usually surrounded, informs us of the minimum speed (in MB/s) of writing guaranteed by the card.

It is key to address the sd Association’s classifications and not the numerical read/write speeds provided by the manufacturer in packaging for several reasons.

For starters, to capture 4K video, the important thing is that the card reaches high write speeds, and in fact, in the market, you can find good models with low reading speeds.

Also, some models inform us of the maximum speed of writing and reading. Look because it is a temporary point peak that can reach the card, not a value that is maintained in a sustained way. For the type of bus used, the maximum speed of cards that only include that classification will be 25 MB/s.

However, when the SDHC and SDXC cards (with a new data transfer bus) were launched, the SD Association introduced a new class, the UHS Speed Class, a reference that you can also find on the card surface original Speed Class.

According to the UHS Speed Class, these are the minimum speeds we can expect:

  • UHS-I Class 1 (U1): minimum speed of 10 MB/s
  • UHS-I Class 3 (U3): minimum speed of 30 MB/s

As for the theoretical maximum speeds, on the U1, we will reach 50 MB/s and on the U3, 104 MB/s. The new UHS-II Class 3 cards have recently been launched, prepared to achieve transfer speeds of up to 312 MB/s but still rare avis on the market, especially in microSD format.

Given its increasing importance in cameras and smartphones, where 4K recording or application installation is common, SD Association has expanded specifications with two more variables, the Application Performance Class and the Video Speed Class:

  • Application Performance Class or ‘APC’ refers to how appropriate a card is for storing application or application data. This class ensures random and sequential write and read speeds suitable for application execution.
  • Video Speed Class tells us how suitable a card is to record video at 4K, 8Kor 360 degrees, and the possibility to allow simultaneous recording of several files. It is represented on the surface of cards with symbols ranging from V6 to V90, where speeds will correspond to 6 MB/s of the V6 at 90 MB/s of the V90, recommended for 8K video.

This table provided by the SD Association is clear: if we want an SD card to capture 4K video, the least will be to go for a Class 10 UHS-I U1 model with V10 Video Speed Class.

However, if the device in question is a camera, we recommend that you also pay attention to other storage systems beyond SD, such as compact flash cards or XQD cards, which are expected to be imposed for video recording because of their higher transfer speed.


Featured models

With the typology, capabilities and clear classifications, it is a matter of looking in the market for those models that meet these characteristics and fit both on our device and our budget.

As we have seen in the previous point, the starting point will be the class 10 UHS-I U1 cards with V10 of 128 GB. However, it is worth looking for models and brands that allow us to climb one more rung for slightly higher investment.