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4K camera lens

How to choose a memory card for shooting 4K video

Of all the devices using digital storage, 4K video cameras may be the easiest to find the best storage solutions for. Despite the high-end capabilities of 4K, its specific needs are so rigid and demanding that finding storage for your 4K video camera is rather easy. There aren’t a lot of variables to make the selection overly difficult.

Before we get to what the important items are in choosing the correct storage, let’s talk a little bit about 4K itself.

The ‘4’ stands for the number four. The ‘K’ stands for thousand. So 4K represents the number 4,000. In this instance, however, it refers to any video resolution with a horizontal pixel count of roughly 4,000.

Why roughly? Well, because the term 4K is used to describe two separate but similar standards. In professional circles such as the Digital Cinema Initiatives (DCI), 4K resolution is 4096 x 2160 and is used for filmmaking. The 4K used in the consumer world (TVs and video equipment) is referred to as Ultra-High Definition (UHD) and has a resolution of 3840 x 2160. So one standard has more than 4,000 pixels, whereas the other does not. Hence, roughly 4,000 horizontal pixels.

With four times the pixel resolution of 1080p, 4K video (both professional and consumer) is clearer, more detailed and amazingly sharper than the HD and Full HD video that was considered so impressive not so long ago. It’s also easier to work with during editing, does not affect image quality after stabilisation processes and allows still images of nearly 8MP to be grabbed.

But it does come with one small hiccup – four times as many pixels may equal a phenomenal image, but it also means double the storage space. For instance, one hour of 1080p digital shooting uses 23GB of space; one hour of 4K video takes 45GB.

DSLR camera with a Kingston Canvas React SD card

When it comes to shooting 4K video, there are four things that really matter: card capacity, write speed, data transfer speed and video speed. And three of them revolve around the same metric. For this discussion, we will be referring to standard-size SD cards and microSD cards.

  • Card capacity: You already know that shooting 4K video leads to excessively large files. We just mentioned that an hour of 4K video uses about 45GB of storage space. Start with 63GB unless you are shooting way less than an hour or are not concerned about running out of space. Card capacities can range up to 256GB and are ideal for 4K video.
  • Write speed: This is probably the most critical factor in selecting 4K storage. Your card choice must have a fast enough write speed to keep up with incoming data. But the choice is easy. SD cards have six different speed classes. Only the U3 class is capable of writing at the speed required for 4K video, which is 30MB/s. Choose only cards that have the U3 marking (the number 3 inside a capital U).
  • Data transfer speed: Pairing your U3-rated SD card with compatible devices that support the UHS bus interface will possibly boost the transfer speeds of your card. Most cameras support the UHS bus interface that UHS memory cards can take advantage of. There is the UHS-I and UHS-II bus interface. UHS-I has theoretical transfer speeds of up to 104MB/s while the UHS-II interface can have theoretical transfer speeds of up to 312MB/s. For U1 and U3-rated SD cards, only the UHS-I bus interface is compatible, while the UHS-II is used by the Video Speed Class memory cards.
  • Video speed: SD memory cards for 4K video storage should have at least a V30 rating/marking, meaning they have the minimum continuous write speed of 30MBs required for 4K. SD cards with Video Speed Class ratings are specifically meant to capture and store video resolutions in 4K or 8K. As the UHS-I bus interface can only support V6 to V30 , the UHS-II bus interface supports V6 to V90 speed class memory cards. The V90 is used in UHS-II mode or faster.

If you’re looking for the best SD card performance you can get for your 4K video, look for UHS-II cards with a V90 rating.

These are all great solutions to the UHS speed class SD cards if your camera requires higher write speeds when recording in 4K or 8K resolution. Having fast enough SD cards with the right write speeds is important, so check with your device owner’s manual to see the required specs for your memory card storage.

Helpful tip: The capacity you choose should be twice as large as what you normally use in 1080p recordings, and the three speed categories (write, data transfer and video speed) are each based on the 30MBs required for 4K recording.

If you need further help in choosing the correct memory card for 4K video, check out our helpful guide explaining the speed classes and write speeds of all our memory cards here.


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