This might sound a bit odd coming from someone who has invested a lot of time and money in speed testing memory cards, but the reality is that your camera probably doesn’t need the fastest memory card you can buy.
And that’s a good thing in this age when demand from the AI industry has been driving up the prices of flash memory across the board. The effects have been cascading down to consumer electronics like cameras for some time now. In late 2025, Micron went so far as to wind down its entire Crucial consumer brand to redirect production toward AI data centers — not a camera-card maker, but a vivid illustration of where the flash supply is going.1
So this is a place where buying smart saves real money.
The key isn’t that you want the fastest card. The key is that you want a card that’s fast enough. This post is about how to work out what that means for your specific camera.
“Fast Enough” means two things
First, a card that can comfortably keep up with the data stream your camera’s video and burst modes throw at it.
Use a card that’s too slow, and you’ll run into genuinely frustrating problems: recordings that stop on their own, the camera locking up, dropped frames, and long waits while the buffer clears before you can shoot again. You want a card that lets you use all of your camera’s features without folding under pressure.
Second, not paying for speed your camera physically can’t use.
There are cameras — mostly flagship bodies pushing high-bitrate 6K or 8K RAW video, or very long RAW bursts — where you really do need blazing speed. But they’re relatively few for now. Most cameras simply don’t need that. If you buy a card that outpaces your camera’s hardware, it will still work and there’s no harm done because backward compatibility is built into these standards. But you’re unnecessarily paying a premium for speed that never gets used.
The bottleneck is the slot
The ultimate bottleneck in a camera is the memory card slot itself. And not all slots are equal.
Put a blazing-fast UHS-II SD card into a UHS-I slot, and you get UHS-I speeds. Drop a cutting-edge CFexpress 4.0 card into a CFexpress 2.0 slot, and you get CFexpress 2.0 speeds. The card’s maximum potential is irrelevant if the slot can’t keep up.
The same logic applies to speed class ratings: if your camera only needs a V30 card, there’s no point forking out for a V90.
A note on dual-slot cameras: many cameras with two slots use mismatched card types — one CFexpress slot paired with one SD slot is a common layout. There are even some, although they’re increasingly rare now, that have the same kind of card (eg. SD) but each is a different bus interface (eg. one slot is UHS-II and the other is UHS-I). In those cases, treat the faster slot as your primary. In some cameras you don’t actually get a choice: the top-end video modes will only work with a specific card type in the primary slot; the shooting mode will be grayed out if you try to use the slower slot.
What the labels actually mean, in numbers
Two things on the card’s label matter here, and they address two different things.
The bus interface (UHS-I, UHS-II, CFexpress) sets the ceiling on how fast data can move at all. It’s describing the actual hardware type.
The video speed class (V30, V60, V90, VPG400) is a guaranteed minimum sustained write speed — the number that decides whether a video recording keeps going. It’s describing, or rather certifying, the card’s practical performance.
Here’s a quick cheat sheet:
| Label | What it guarantees or allows | Typical use |
|---|---|---|
| UHS-I | Bus ceiling of about 104 MB/s | Most entry and mid-range cameras, compacts, many older bodies |
| UHS-II | Bus ceiling of about 312 MB/s | Enthusiast and pro bodies; needed for V60/V90 cards to reach their potential |
| CFexpress Type A / Type B (2.0) | Roughly 1,000 / 2,000 MB/s ceilings | High-bitrate RAW video and deep bursts in pro bodies |
| CFexpress 4.0 | Roughly doubles 2.0 speeds | Newest flagships; older CFexpress slots run it at 2.0 speeds |
| V30 | Minimum 30 MB/s sustained write | 4K up to about 200 Mbps |
| V60 | Minimum 60 MB/s sustained write | 4K at high frame rates, roughly 200–400 Mbps |
| V90 | Minimum 90 MB/s sustained write | Very high bitrates, 6K/8K, RAW video on SD |
You’ll notice that the speeds above are using MB/s (megabytes per second. That matters, and it’s somewhere that can become confusing.
Cameras quote video bitrates in megabits per second (Mbps), while cards are rated in megabytes per second (MB/s). Divide by eight. A 4K recording at 100 Mbps writes about 12.5 MB/s — trivial for a V30 card. At 200 Mbps it’s 25 MB/s, still within V30’s guarantee. At 400 Mbps it’s 50 MB/s, and you want V60. Push past 600 Mbps, as RAW video formats do, and you’re into V90 or CFexpress territory. (If you want to skip the mental arithmetic, I have a Mbps-to-MB/s converter to make it easy, and I go deeper on the ratings in my guide to SD card speed classes and UHS-I vs UHS-II explainer.)
How to read your camera’s spec sheet
There are three things to look for in the specifications. You’ll find them in the manual, on the manufacturer’s site, or in any thorough review.
- The slot interface. Look for “UHS-I,” “UHS-II,” or “CFexpress Type A/B” in the storage line. This is the camera’s hardware ceiling — no card can go faster in that slot.
- The maximum video bitrate (or the highest-quality video format, like ProRes or N-RAW). Convert it to MB/s and match it to a V; add a little wiggle room for the natural overhead you get when using a memory card in practice.
- Any card requirement the manufacturer attaches to a specific mode. Some bodies flatly require a V60 or V90 card, or a CFexpress card in slot 1, for their top video modes. If that’s printed in the manual, it’s not optional. But in some cases it only applies to specific shooting modes or features.
A few worked examples from cameras I’ve written specific recommendations for:
- Fujifilm X100VI: a single UHS-I slot and a 200 Mbps video ceiling. A V30 UHS-I card covers everything it can do; a pricier UHS-II V90 card works, but runs at UHS-I speed and buys you nothing in camera.
- Canon EOS M50: same story — UHS-I slot, so a fast UHS-II card is wasted money for shooting.
- Canon EOS R8: a single UHS-II slot and 4K60 video, so this is a camera where stepping up to a UHS-II V60 or V90 card genuinely pays off.
- Nikon Z50 II: UHS-II slot with N-RAW video on tap. A UHS-I V30 card works for stills and modest video but limits the top video modes; V60/V90 UHS-II unlocks them.
- Nikon Z6 III: one CFexpress Type B slot and one UHS-II SD slot. Its 6K RAW video needs CFexpress in slot 1 — the SD slot can’t do that job no matter how fast the SD card. Here, buying the right type matters more than buying the fastest card.
When faster really is worth it
To be clear, I’m certainly not saying never to buy the fastest memory cards. Some cameras genuinely do need them. Specifically:
- High-bitrate RAW or ProRes video. 6K/8K and RAW formats routinely exceed 600 Mbps, and the card has to sustain that without a hiccup. This is the main reason V90 and CFexpress exist.
- Long bursts. A faster card clears the buffer sooner, so you’re shooting again sooner. If you regularly hold the shutter down on sports or wildlife, that’s tangible.
- Offloading. In-camera limits don’t apply at your desk. With a UHS-II or CFexpress card, a matching reader, a proper cable, and a modern port, you get the card’s full read speed when copying to your computer — and if you move a lot of RAW files or video, that difference is real and noticeable. The chain still runs at the speed of its slowest link, but if every link is fast, the faster card is doing something useful.
- A planned upgrade. If you’re about to move to a body with faster slots, buying the faster card now avoids buying twice. If that upgrade is hypothetical, buy for the camera you own.
Matching the card to the camera
So it’s worth taking a close look at your camera’s actual specs before buying. If it has a UHS-I slot, a more expensive UHS-II card won’t give you better in-camera performance. If it needs V30, a V90 is overkill. And if it has a CFexpress slot for its top modes, the card type matters more than the speed number on the label.
There’s a reason I’ve put a lot of effort into matching memory card recommendations to specific cameras. Blanket advice to “just buy the fastest card you can” is a good way to waste money.
What you actually want is a card that’s fast enough — and that means knowing what your camera’s real bottlenecks are. If you do want to see which cards are genuinely the quickest, my independent SD card speed tests cover that too — just don’t buy from the top of that list unless your camera can use it.
