The one whose published speed class meets what the camera asks of it, in the slot format the body accepts. Both facts are published per body, and the card’s own headline speed is the least useful figure printed on it.
A card choice is two published facts on the camera side, and one on the card side.
The two facts on the body
The slot format, which is not negotiable, and the minimum class the body asks for in its recording modes. Both come from the camera’s own documentation, and a body that records at a high bit rate states a requirement there rather than leaving it to the buyer.
The figure to read on the card
The speed class marks, not the headline. Those small symbols describe a minimum sustained write speed, which is what a camera writing video actually depends on. In this catalogue the card vocabulary is thin — memory cards belong to a neighbouring site rather than to this one, which is why our listings mention a card only when a bundle includes one.
What no figure covers
How long a card lasts, and how it fails. Neither is published in a comparable form, which is the practical argument for two cards rather than one large one. That is a habit rather than a specification, and this site does not dress it as anything else.
What people ask before they commit
Is the big number on the front of the card the one that matters?
Rarely. That figure is a peak read speed under ideal conditions. What a camera needs is a sustained write speed, and that is what the speed class marks describe — the small symbols beside the capacity. A card with a large headline number and a low class mark can still stutter while recording.
Will a faster card make my camera quicker?
Only up to what the body can use. A camera writes at the rate its own controller allows, and a card faster than that ceiling changes nothing inside the camera — though it may still save time when you copy the files off it afterwards, which is a different benefit with a different figure behind it.
Last reviewed 12 September 2026