Where things can become confusing is when you see SDHC and SDXC.
The first stands for Secure Digital High Capacity.
This was initially introduced to cover SD cards with a capacity above 2GB and below 32GB.
The latter stands for Secure Digital eXtra Capacity, which go far beyond 32GB in size.
you’re free to buy SDXC cards with a whopping 2TB of storage.
Problems might arise depending on the gear youre looking to use them in.
Devices are backwards compatible, so an SDXC-compatible gadget can use SDHC and SD cards.
An SDHC-compatible machine can use SDHC and SD cards, but will not be able to use SDXC cards.
you’re free to also find miniSDHC cards, which expanded storage to 4GB.
Again, youll need to check that your unit specifically supports miniSDHC rather than just miniSD.
The miniSD card never gained much traction, however, so devices that use it are relatively uncommon.
The microSD is the smallest version.
You might have also seen it referred to as TransFlash or abbreviated as a TF card.
When buying a microSD, microSDHC or microSDXC card youll usually get a full-size SD card adaptor as well.
The next area of confusion is around speed classes.
These are how different SD, miniSD and microSD cards are rated in terms of read and write speeds.
High-resolution and high bit rate video requires a lot of data to be written to the card very quickly.
Still cameras with high resolutions and fast burst shooting will also take modern cards to their limits.
TheSD Associationdevised a way to standardise the speed ratings for different cards.
These are defined as Speed Class and refer to the absolute minimum sustained write speeds.
Many SD card manufacturers will also list a specific speed alongside the Class rating.
This means a card can be Class 10 but also be listed as up to 80MB/s.
You might also see a description such as 533x.
This refers to a multiplication of the speed of an old CD-ROM (150KB/s).
So in this case 533 x 0.15 = 80MB/s (as there are 1,000KB in a MB).
The next rating is the UHS Speed Class.
This stands for Ultra High Speed and refers to minimum sustained writing performance for recording video.
UHS came about due to 4K-capable video devices needing faster write speeds.
The SD Association has two UHS Speed Classes, UHS Speed Class 1 and UHS Speed Class 3.
The UHS Speed Class is denoted by either a 1 or 3 inside of a bucket U symbol.
As a rule of thumb, 4K-capable camcorders will usually require at least a U3 rated SD card.
Theyll be listed as either UHS-I or UHS-II to show which interface is used.
Note, that unlike the UHS Speed Class, these are not sustained speeds.
If youre not recording in 4K, the speed might not be so important.
Class 10 cards are usually not much more expensive so its worth paying the extra.
source: www.techworm.net
