Photography & Camera Gear / Guide
How to Choose an SD Card Speed Class for Camera Video
Match your camera’s recording mode to an SD card’s speed class, check UHS compatibility, and size the card using bitrate and recording time.
When you buy a memory card for video, start with the camera’s recording menu. Write down the resolution, frame rate, compression option and bitrate you plan to use. Two modes that both say 4K can ask very different things of the card. Then open your camera’s manual and find the card requirements for that exact mode.
Read the speed class and the bus label separately
The SD Association’s Video Speed Class describes minimum sequential write performance under the standard’s conditions. V30, V60 and V90 correspond to minimums of 30, 60 and 90 MB/s. A large number printed next to “up to” on the packaging can be a peak read figure. It helps explain how fast transfers might be under favorable conditions, but it doesn’t replace the class the camera calls for.
UHS-I and UHS-II describe the bus interface. Check which interface the camera and your reader support. An older reader can limit transfer speed even if the camera and card can record together just fine. Also confirm the camera accepts the card capacity and format you’re buying. The Fujifilm X half, for example, lists UHS-I in its specifications.
Estimate capacity from the bitrate
Divide megabits per second by eight to get megabytes per second. At 200 Mb/s, the arithmetic gives about 25 MB/s, or 1.5 GB per minute. Half an hour at that rate takes roughly 45 GB before allowing for overhead, variable bitrate or space you want to leave free. Use this calculation to choose capacity. For the required speed class, follow the manual, which accounts for how the camera writes the files.
A spare card can make more sense than moving up to a single larger one. If you normally record one segment at a time, two compatible cards let you set the first aside after a take. If you shoot long, uninterrupted events, prioritize a card that holds the entire expected segment with margin.
Test the recording mode before the job
Buy from a seller you trust and keep the packaging until you have tested the card. Back up anything on it, format it using the camera’s instructions and record in the exact mode you intend to use for long enough to cover a typical take. Play back the clip and copy it through the reader you’ll take on the job. This gives you a chance to spot a card error, a recording limit or a slow ingest before any of those problems cost you a shot.
