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CFexpress vs SD UHS-II: Which Card Your Camera Actually Needs

Short answer

A fast V90 SD UHS-II card sustains around 90 MB/s minimum, which handles ordinary 4K recording up to roughly 700 Mbps. CFexpress sustains several hundred megabytes per second and is what unlocks the highest bitrate intraframe and RAW modes. If your camera takes both, start on SD and add CFexpress when you find a mode SD cannot hold.

This decision is made by your camera far more than by you, and the useful question is whether you need the expensive card at all. A Delkin 512GB CFexpress Type B 4.0 at around $280 unlocks every mode your body offers. A fast V90 SD card costs a fraction of that and handles ordinary 4K recording perfectly well, which on a body with dual-format slots is a genuine way to spread the cost.

The formats, briefly

SD UHS-II uses a second row of contacts to roughly triple the bandwidth of UHS-I, and its video speed classes are the useful ratings. V60 guarantees 60 MB/s minimum sustained write, and V90 guarantees 90 MB/s. Those are minimums rather than peaks, which makes them far more meaningful than the large numbers printed on the front of the card.

CFexpress uses PCIe and NVMe, the same technology as an internal computer drive. Type A uses one PCIe lane and Type B uses two, so Type B is roughly twice as fast. Sustained rates in the hundreds of megabytes per second are normal, and the good cards hold those rates rather than dipping.

The physical formats are unrelated, so a camera takes what it takes. Many bodies now have dual-format slots that accept either an SD card or a CFexpress card in the same physical slot, which is what makes this a real choice rather than a fixed constraint.

The comparison

SD UHS-II V90CFexpress Type B
Minimum sustained write90 MB/s guaranteed400 MB/s and up on good cards
Maximum bitrate supportedAbout 700 MbpsSeveral thousand Mbps
Cost per 512 GBAbout $150 to $250About $280 to $400
Physical robustnessThin, easy to lose, exposed contactsThicker, metal shell, recessed contacts
Heat behaviourWarm, moderate throttlingHot, real throttling under load
Offload speedAbout 300 MB/s read1,700 MB/s and up read
SuitsOrdinary 4K, long-GOP, most delivery workHigh bitrate intraframe, RAW, 8K

The offload row is a real quality of life difference nobody mentions when comparing formats. Clearing a 512 GB CFexpress card takes a few minutes with a fast reader; the same capacity of SD takes closer to half an hour. Across a shoot with several cards that is most of an evening.

The maths that decides it

Divide your camera bitrate by 8 to get megabytes per second. A 240 Mbps all-intra mode needs 30 MB/s sustained, which a V60 SD card handles comfortably. A 600 Mbps mode needs 75 MB/s, which is inside V90 with very little margin. A 1,200 Mbps mode needs 150 MB/s, which no SD card sustains.

That is the whole decision. Look at the modes your camera offers, find the highest bitrate you actually intend to use, do the division, and add real headroom rather than buying a card rated exactly at the requirement. The recording bitrate calculator does this and reports which card class each mode needs.

The trap is buying for a mode you never use. Many people buy CFexpress for an 8K RAW mode they will shoot twice, and then spend three times as much per gigabyte on every card for the rest of the camera's life. If your actual work is 4K 10-bit long-GOP, SD is genuinely sufficient.

CFexpress, in both types

$194 to $400. Type B for most cameras, and Type A for Sony cine line bodies that take that format instead.

Best value $279.99
Delkin 512GB CFexpress Type B 4.0

Delkin Devices

Delkin 512GB CFexpress Type B 4.0

512 GB of CFexpress 4.0 at the lowest sane price per gigabyte, which matters because RAW eats cards faster than any other format decision.

Capacity
512 GB
Spec
CFexpress 4.0 Type B

The value card for most cine bodies.

Check price

The Type A problem

Sony cine line bodies including the Sony FX3, Sony FX30 and Sony FX6 use CFexpress Type A, not Type B. Type A is physically smaller, uses a single PCIe lane, and costs substantially more per gigabyte because the market is smaller and Sony is effectively the only customer.

Those same bodies take SD UHS-II in the same dual-format slots, which is what makes the SD-first strategy genuinely practical on a Sony. A Lexar 256GB CFexpress Type A Silver 4.0 at around $194 for 256 GB is the value entry into Type A, and starting on SD and adding one card later is a reasonable way to spread that cost.

This premium is worth counting when comparing camera bodies, because it appears on every card you buy for the life of the camera. It is a real ownership cost that never shows up in a camera review.

Heat, and why cards fail mid-take

CFexpress cards run hot, and a hot card reduces its write speed to protect itself. In a camera that already runs warm, on a hot day, inside a cage that traps heat, a card that sustains 400 MB/s on a bench can fall below that in the field. It fails in exactly the mode that needed the speed.

It usually appears as a recording that stops rather than a corrupted file, which is the good news. The bad news is that it stops when the bitrate spikes, and the bitrate spikes when something complex and interesting happens in frame.

This is one of the things a higher price genuinely buys. Cards with a metal shell and better thermal design hold their rate longer, and on a body known to run warm that difference is worth paying for rather than economising on.

The verdict

  • Camera takes only CFexpress: buy CFexpress, 512 GB, and size the capacity to a shoot day.
  • Camera takes only SD: buy V90 for all-intra modes, V60 is fine for long-GOP.
  • Dual-format slots and ordinary 4K work: start on SD, and add CFexpress when a mode you want needs it.
  • RAW or 8K modes you genuinely shoot: CFexpress, with headroom rather than a card rated exactly at the requirement.
  • A Sony cine line body: budget for the Type A premium, and use SD in the meantime.
  • Two 512 GB cards, always, rather than one 1 TB card, so a loss costs half a day.

One rule crosses both formats: a card is not a backup. Offload to two separate drives every night, verified, and never format in the field to make room. A spare card costs less than reshooting anything, and formatting to continue is the moment a day exists in exactly one place.

Next, from here

Common questions

Do I need CFexpress or is SD enough?
Divide your camera bitrate by 8 to get megabytes per second. A V90 SD card guarantees 90 MB/s sustained, which covers modes up to roughly 700 Mbps including ordinary 4K and most all-intra recording. CFexpress is what unlocks the highest bitrate intraframe and RAW modes. If your work is 4K 10-bit long-GOP, SD is genuinely sufficient.
What does V90 mean on an SD card?
It is a video speed class guaranteeing a minimum sustained write of 90 MB/s, which is far more useful than the large peak numbers printed on the front. V60 guarantees 60 MB/s. Those minimums are what determine whether a card can hold a recording mode without dropping frames, since peak speeds are burst figures into a cache.
Why is CFexpress Type A so expensive?
Because the market is small and Sony cine line bodies are effectively the only customer. Type A uses a single PCIe lane against Type B's two, so it is slower as well as costlier per gigabyte. It is a real ownership cost of a Sony cine body that appears on every card for the life of the camera and never shows up in a camera review.
Why does my camera stop recording mid-take?
Usually the card throttled from heat. CFexpress cards run hot and reduce write speed to protect themselves, which drops them below what a high bitrate mode needs, and it happens when the bitrate spikes because something complex is in frame. It appears as a stopped recording rather than a corrupted file. Better thermal design is one thing a higher price genuinely buys.
Should I buy one large card or two smaller ones?
Two 512 GB cards rather than one 1 TB card. They cost less per gigabyte on most product lines, and a failure or a loss then costs half a shoot day rather than all of it. Five hundred and twelve gigabytes is roughly five hours at 240 Mbps and close to two hours at high bitrate all-intra, which covers a working day.
Can I mix SD and CFexpress in a dual slot camera?
Yes on bodies with dual-format slots, and it is a sensible way to spread cost. Use SD for ordinary modes and put a CFexpress card in when a specific high bitrate mode needs it. Note that relay and backup recording across two different formats will be limited by the slower card, so simultaneous backup recording may cap your available modes.

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How this page was researched. Specs come from manufacturer documentation, published payload and power ratings, and verified owner reviews. We do not claim to have had every one of these items in our hands, and we will not pretend otherwise.

This is researched guidance, not professional advice. Both formats throttle when hot. A card that sustains its rated speed on a bench may not in a warm camera in the sun.