What is the Next-Generation Memory Card CFexpress?

CFexpress is a new recording media standard that integrates the previous XQD and CFast formats, developed by the CompactFlash Association (CFA), of which SUNEAST is a member.

In 2017, when the CFexpress 1.0 standard was established, the theoretical speed of Type B cards—designed for cameras—was 2,000MB/s, more than six times faster than SD UHS-II cards. This impressive speed and reliability have been highly praised, making CFexpress the standard memory card for high-resolution, high-speed burst cameras. Many flagship cameras from leading manufacturers now use CFexpress as their primary recording medium.

Sizes of each type

CFexpress inherits the size of XQD and includes Type B, used in cameras and offered by SUNEAST, as well as the smaller Type A and the larger, business-card-sized Type C. The reason for offering multiple sizes (A, B, and C) is to ensure compatibility with various devices beyond 35mm full-frame cameras (which typically use Type B). This approach aims to improve development and production efficiency while reducing costs in the future.

CFexpress Specifications and Future Development

CFexpress uses the PCIe interface and the NVMe protocol, which are highly versatile and widely used in PC SSDs. This ensures ease of component procurement and allows for further speed improvements, making CFexpress a highly scalable standard for the future.

	Interface	Protocol	Theoretical Transfer Speed per Lane	Theoretical speed for Type B (2-lane)
CFexpress 2.0	PCIe 3.0	NVMe 1.3	1,000MB/s	2,000MB/s
CFexpress 4.0	PCIe 4.0	NVMe 1.4c	2,000MB/s	4,000MB/s

Since Type B is standardized with the same size and terminals as XQD, it is backward compatible, and in some cases, can be supported through a firmware update on the camera. Please check the manufacturer’s website for further details.

CFexpress Type B cards mainly use two types of flash memory: TLC and pSLC.

TLC (Triple-Level Cell) technology records 3 bits per cell, making it possible to achieve larger capacities at lower costs. However, the process of reading and writing data is more complex, which historically compromised speed performance. Recently, though, products with sufficient speed performance have been developed.

On the other hand, pSLC (Pseudo-Single-Level Cell) technology enhances reliability and speed by limiting the data recorded per cell to 1 bit, even though it uses multi-level cells like TLC. pSLC also reduces the electrical load on the cells, improving rewrite performance and allowing up to 30,000 rewrites.

For users prioritizing reliability, speed, and durability, pSLC is often chosen, while those seeking cost performance tend to opt for TLC.

In actual shooting, ‘sustained transfer speed’ is an important performance indicator. The ‘sustained transfer speed’ refers to a speed class that guarantees a minimum speed, such as V60 for SD cards.

When shooting high-bitrate videos like 4K or performing high-speed continuous shooting, this sustained transfer speed directly affects the smoothness of the shooting experience, so it’s crucial to choose the right card based on your shooting needs.

Approximate Data Storage Capacity on an CFexpress Card

	128GB	160GB	400GB	640GB	1600GB	2TB
20 million pixels JPEG Approximately 20MB	Approximately 6,550 photos	Approximately 8,190 photos	Approximately 20,480 photos	Approximately 32,760 photos	Approximately 81,920 photos	Approximately 104,850 photos
20 million pixels RAW Approximately 50MB	Approximately 2,620 photos	Approximately 3,270 photos	Approximately 8,190 photos	Approximately 13,100 photos	Approximately 32,760 photos	Approximately 41,940 photos
FULL HD（1920×1080@30fps） 50Mbps	5 hours and 50 minutes	7 hours and 17 minutes	18 hours and 12 minutes	29 hours and 8 minutes	72 hours and 49 minutes	93 hours and 12 minute
4K（3840×2160@30fps） 100Mbps	2 hours and 55 minutes	3 hours and 39 minutes	9 hours and 6 minutes	14 hours and 34 minutes	36 hours and 24 minutes	46 hours and 36 minutes