Do not choose a camera card from the large advertised read-speed number alone. Start with the write class required by your recording mode and the card types your camera supports.
What to check first
Under SD Association conditions, V30 and U3 both indicate a minimum sequential write speed of 30 MB/s. Equal numbers do not remove the need to match the speed-class symbol required by the host. Peak read speed is not a substitute for sustained video-writing performance.
A worksheet you can use
Put the camera manual beside the card specification and complete these fields before buying.
| Item | What to record |
|---|---|
| Recording mode | Resolution, frame rate, codec and bitrate |
| Required class | The V or U class symbol specified by the manual |
| Card type | Supported SDHC or SDXC type and capacity range |
| Interface | The UHS interface supported by the camera |
| Exact card | Model, capacity and class markings |
Check in this order
- Find the memory-card requirement for the exact mode you will record
- Match the required class system and also check capacity and interface support
- Back up existing files, prepare the card as the camera manual directs, and make a short recording and playback check before an important shoot
If the problem remains
If recording stops, note the camera error, card model and mode before buying a pricier card. Check the manufacturer’s compatibility list and support route. Do not format a card that still holds footage you need.
Related guide
Does a Highly Rated Product Fit You? A Review Evidence Worksheet
A worked example
Hypothetical example: the manual requires V30. A card carrying only U3 has the same numerical minimum, but that alone does not establish compliance with the camera’s V30 requirement. Confirm the required marking before purchasing.