“SD” What does it means ?
“SD” is a short for: “Secure Digital”, which is an electronic memory data storage device that can store a significant amount of data depending on its size. This card was developed by the SD Association to be used in portable devices, such as : Digital Cameras, Camcorders, Video Game Consoles, Mobile Phones, Action Cameras (GoPro Hero series) and Camera Drones.
The SD memory cards are most commonly used to store the photos that all type of photographers captures through their camera or the videos that they shoot.
SD Card Capacity Types
SD cards currently come in five families describing memory capacity ranges:
- miniSD (Standard SD cards (SDSC)) :
The SD standards are a timeline of the evolution of SD cards with newer cards allowing higher capacities and speeds.
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Capacity
Min: 0 , Max: 2 GB
File System
FAT 12 / FAT 16
- microSD (also called T-Flash or TF or TransFlash card) :
The microSD cards are the smaller-sized version of SD cards and the biggest difference between the two is the form factor. They’re also more versatile since they’re often available with an SD adaptor that allows you to use microSD cards in hardware devices that only support SD cards.
They are more commonly used to expand the storage system of smartphones, cameras, drones and gaming devices.
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Capacity
Min: 0 , Max: 2 GB
File System
FAT 12 / FAT 16
- SDHC (High Capacity) :
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Capacity
Min: from 2 GB ,
Max: 32 GB
File System
FAT 32
- SDXC (Extended Capacity) :
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Capacity
Min: from 32 GB ,
Max: 2 TB
File System
exFAT
- SDUC (Ultra Capacity) :
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Capacity
Min: from 2 TB ,
Max: 128 TB
File System
exFAT
Understanding SD Card Labeling and Specifications:
SD cards provide on the front of the card a lot of information, so what we expect to know:
“SD card speed is rated by its sequential read or write speed”.
The early SD card manufacturers, specified the speed as a "times" ("×") rating, which compared the average speed of reading data to that of the original CD-ROM drive.
The SD Association came up with a way to standardize the speed ratings for memory cards. They define standard speed classes for SDHC/SDXC cards indicating minimum performance. Both read and write speeds must exceed the specified value.
The SD Associationdefines three types of Speed Class ratings:
- The original Speed Class :
The graphical symbol for the speed class has a number encircled with 'C'
There are four ratings within this speed class:
1 -
C2 (Class 2): minimum write speed of 2MB/s
2 -
C4 (Class 4): minimum write speed of 4MB/s
3 -
C6 (Class 6): minimum write speed of 6MB/s
4 -
C10 (Class 10): minimum write speed of 10MB/s
- UHS Speed Class (Ultra-High Speed) :
The graphical symbol for the UHS speed class has a number inside the 'U’
There are two ratings within this speed class:
1 -
U1 (UHS Speed Class 1): minimum write speed of 10MB/s
2 -
U3 (UHS Speed Class 3): minimum write speed of 30MB/s
What makes the U1 and U3 memory cards more advanced than those in the Speed Class are that they use one of two UHS bus interfaces:
1 - UHS-I: theoretical maximum transfer speeds up to 104MB/s
2 - UHS-II: theoretical maximum transfer speeds up to 312MB/s
- Video Speed Class :
The graphical symbols use a stylized 'V' followed by a number.
There are five ratings for the Video Speed Class:
1 -
V6 (Video Speed Class 6):
minimum write speed of 6MB/s
2 -
V10 (Video Speed Class 10):
minimum write speed of 10MB/s
3 -
V30 (Video Speed Class 30):
minimum write speed of 30MB/s
4 -
V60 (Video Speed Class 60):
minimum write speed of 60MB/s
5 -
V90 (Video Speed Class 90):
minimum write speed of 90MB/s
- Application Performance Class :
is a new classification has been presented with the introduction of Android’s Adopted Storage Device feature. This Class assures minimum random and sequential performance speeds to meet both run and store execution time requirements under given conditions. It does this simultaneously while providing storage for pictures, videos, music, files and other important data.
The graphical symbols use a stylized 'A' followed by a number.
There are two ratings for the App Performance Class:
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A1 has a minimum random read of 1500 IOPS and a minimum random write of 500 IOPS.
*
A2 has a minimum random read of 4000 IOPS and a minimum random write of 2000 IOPS.
Both A1 and A2 have a minimum sustained write speed of 10MB/s.
The newer families of SD card improve card speed by increasing the bus rate (the frequency of the clock signal that strobes information into and out of the card). Whatever the bus rate, the card can signal to the host that it is "busy" until a read or a write operation is complete.
Bus interface types:
- Default Speed : SD cards will read and write at speeds of 12.5 MB/s.
- High Speed : SD cards will read and write at speeds of 25 MB/s.
- Ultra High Speed (UHS) : bus is available on some SDHC and SDXC cards.
Cards that comply with UHS show Roman numerals 'I', 'II' or 'III' next to the SD card logo, they are usually written out as “UHS-I” and “UHS-II,” but many card manufacturers are omitting the UHS lettering and simply using a “I” or “II” symbol to indicate the type of UHS bus interface on the card.
The following ultra-high speeds are specified:
- UHS-I
- UHS-II
- UHS-III
- SD Express
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