Memory-card labels can look like alphabet soup. The important thing is to separate capacity, bus type, and minimum sustained write speed.
V30, V60, and V90
The Video Speed Class number describes a guaranteed minimum sustained write speed in megabytes per second.
- V30: at least 30 MB/s sustained write speed.
- V60: at least 60 MB/s sustained write speed.
- V90: at least 90 MB/s sustained write speed.
UHS-I vs UHS-II
UHS-I and UHS-II describe the card interface. UHS-II cards have a second row of contacts and can support much faster transfers when the camera and card reader also support UHS-II.
A UHS-II card can often work in a UHS-I slot, but it will operate at the slower interface speed. Buying a faster card does not make a camera exceed the limits of its own card slot.
Do all 4K cameras need V60 or V90?
No. Resolution alone does not determine card requirements. Bitrate and recording format matter. Some 4K modes work comfortably on V30 cards, while high-bitrate intraframe recording or very high frame-rate modes may require much faster media.
Use the camera manual, not a generic rule
The best source is the camera manufacturer’s recording-media table. Match the card class to the exact resolution, frame rate, codec, and bitrate you plan to use.
Real camera examples
- Canon EOS R50 memory-card requirements
- DJI Osmo Pocket 3 microSD requirements
- Sony ZV-E10 II V30, V60, and V90 requirements by recording mode
- GoPro HERO13 Black microSD requirements
Why card speed matters for still photography too
Fast cards can help clear the camera buffer more quickly during long bursts. The practical benefit depends on the camera’s own card interface and write speed.
Capacity is a separate question
A fast card can still be too small for a long shoot. Use bitrate and card capacity together when planning video storage.
See why bitrate changes file size.
Estimate how much 4K video fits on common card sizes.
Shopping rule
Buy enough speed for your hardest recording mode, then prioritize reliability and adequate capacity. Paying for a much faster card than the camera can use may not improve shooting performance.