Why Sony Chose CFexpress Type A Cards for the a7S III

When there's money to be made companies will look for a leg up anywhere they can. With the announcement of the a7S III, Sony has sidestepped the popular and faster CFexpress Type B cards, and instead, included CFexpress Type A on its latest full-frame mirrorless camera. 

Just as SD cards are available in miniSD, microSD, and SD, the CompactFlash Association created standards for CFexpress that includes three different sizes. Type A, Type B, and Type C. Manufacturers like Delkin, Lexar, ProGrade Digital, SanDisk, and Sony have saturated the market with affordable Type B cards, but the introduction of Type A on the a7S III puts Sony in the market first. 

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CFexpress Type A cards are slightly smaller and substantially slower than CFexpress Type B – about half the speed – but still have plenty of power to record 4K at high bit rates. 

• Type A: Speeds up to 1000MB/s
• Type B: Speeds up to 2000MB/s
• Type C: Speeds up 4000MB/s

The Sony Alpha line has always been SD card friendly, and with the a7S III, Alpha steps into CFexpress. But don't fret, the a7S III features dual card slots that are still compatible with SD UHS II and UHS I cards. Sony has just added CFexpress Type A into the mix and might provide a glimpse to where the company is headed. 

So why did Sony go with CFexpress Type A?

Most likely for a number of reasons. The company has a long history of paving it's own path when it comes to memory cards dating back to 2007 when Sony released the HDR-CX7 with a memory card stick. Since, shooters have seen different types of SxS and Pro SxS cards as well as XQD cards for cameras like the FX9, a format owned by Sony. Essentially, Sony wants to carve out a part of the market for themselves since they develop their own memory cards. But it also allows the a7S III to use one slot for both Type A and SD cards because of how close they are in size. The SD cards point one way, the CFexpress cards point another way. 

Sony a7S III shooters won't have to worry about the slower CFexpress Type A card with the camera as the camera only writes data so fast. Both SD and Type A memory cards allow for 4K 120p, ALL-I recording, and over 1,000 uncompressed RAW images. But on top of that, the Sony a7S III allows the memory cards to simultaneously record, relay record (card to card), or sort record. Meaning, one card can be all video, the other card can be all images or different formats, which is a nice touch.

Where the difference comes in for Type A and Type B cards is in the read and write speeds when transferring media to another device. Type A caps out at 1000MB/s, so you won't find companies offering anything higher. Right now, there are Type B cards with speeds higher than 1400MB/s from Delkin and ProGrade Digital.