How to Choose a Memory Card (SD, CFexpress...)

A memory card can seem like a minor accessory — until it slows down your burst rate mid-assignment, or worse, corrupts an entire day’s shoot. Choosing it carefully avoids both of these bad surprises.

Write speed, the real technical criterion

Write speed determines how quickly the camera can clear its buffer onto the card — far more decisive for burst shooting and video than total capacity. Speed classes (V30, V60, V90 for SD cards) indicate a guaranteed minimum throughput : V30 covers most photo uses, while V60 or V90 become useful for intensive bursts or high-resolution video.

Capacity, a question of spreading the risk

A single very high-capacity card risks losing everything at once if it fails — spreading your shots across several medium-capacity cards limits the damage if one of them causes a problem. A dual-slot camera set to write simultaneously to both cards offers the best immediate protection against a card failing mid-session.

Brand, more important than the lowest price

Counterfeit or dubious-quality memory cards circulate widely on discount online marketplaces, with a real risk of corruption or a capacity that doesn’t match what’s advertised. Sticking to well-known brands, bought from a reliable retailer, remains the best guarantee — a memory card is never the place to cut corners on a photography budget.

The format suited to your camera

Most common mirrorless and DSLR cameras use SD cards, while recent professional bodies increasingly adopt the CFexpress format, faster but also more expensive. Checking the format and maximum speed your own camera can actually use avoids investing in a card more capable than what the body can exploit — and remember that a memory card remains, in every case, a transport medium, never a long-term storage solution.