Understanding SD Cards nomenclature!

This is a quite confusing topic

SD cards have basically 2 specs, capacity and speed —but there are actually two types of speed that matters.

The storage capacity and card format, initial SD cards had 128MB to 2GB, formatted in FAT16, then came the SDHC with capacity from 4GB to 32GB, formatted in FAT32 and now SDXC, which supports from 64GB up to 2TB and it’s formatted in exFAT.

I’m not even sure why they sticked with FAT32 for so long, FAT32 is a very old format, in a time that 4GB was too much and FAT32 can’t handle files bigger than 4GB.

The highest capacity SDXC so far is the just announced 1TB SDXC from SanDisk, soon enough they will achieve 2TB and I’m not sure if there will be a new format or if some other already existing format will be adopted by manufacturers and become the new standard.

The second spec is the Speed Class, like UHS-I and UHS-II and they measure the Bus Speed, so that’s usually the maximum writing and reading speed you see in some cards. UHS-II cards can be around 3x faster than UHS-I cards.

The problem is that for video it’s not the Bus Speed that matters but the Minimum Sequential Write Speed. To measure that, they created the U1, which has minimum of 80mbps (10MB/s) and U3, 240mbps (30MB/s).

So you basically have two Speed Classes depending on what you need, one for Bus Speed and another for Video. It was getting confusing so they decided to create a new video standard, V6 (6MB/s), V10 (10MB/s), V30 (30MB/s), V60 (60MB/s) and V90 (90MB/s).

So V6 is the same as Class 6, V10 is the same as Class 10 and U1, and U3 is the same as V30!

That’s not confusing at all!

To help with that there are also other new high-speed cards standard like Sony’s XQD and Samsung’s UFS!

Edit: September, 28th

After doing more research for another article, I came to the conclusion that:

1. There is no card that has V60 or V90 standard but there are cards that can actually record higher speed — remembering that V60 and V90 are about Minimum Sequential Write Speed and not Maximum Sequential Write Speed — so it means that their maximum speed exceeds both 60MB/s and 90MB/s. As for why it doesn’t guarantee a V60 and V90 standard, I’ve no idea.
2. The good is that we know that there are cards that can be faster, the bad is that by not complying to the standard, the only way to know if the card is capable of sustaining those bit rates is by doing tests and that sucks since you have to rely on other people. Most mortals won’t be able to simply buy all sort of expensive cards and test all of them just to share which one can do what, so we need to rely on manufacturers recommendations and 3rd parties like bloggers, Youtubers and specialized media that are willing to do all the tests and publish it.
3. The V60 and V90 standard is yet to be adopted but there are already products demanding something faster than 90MB/s, so the standard barely exists but in some ways it’s already outdated. So maybe in the near future more letters and numbers will be added to the already confusing Class Speed standard.