Some considerations on SD cards

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Here is the useful information about SD cards (usually used in cameras, surveillance cameras, videocameras, smartphone and tablets).

What is the SD Speed Class?

When we go at a technology market we see a lot o acronyms and brands about SD cards and their specifications. What they means? For example, what's the difference between an SD and an SDHC card? My camera will be able to use an SDHC card?

The SD Association has established standards that rate the minimum data transfer in SD, SDHC, SDXC, SDHC UHS-I and SDXC UHS-I memory cards and devices. The speed rates were established based on the needs of movie and video companies because video recording requires certain writing speeds when recording the data onto a memory card. The SD Speed Class and UHS Speed Class standardized the specification for both memory cards and devices in order to guarantee minimum writing speeds and deliver the best performance.

What are the applications for Speed Class?

Class 1 : even called UHS class (Ultra High Speed), is the fastest class available and it's not available on SD cards, but only on SDHC and SDXC cards.
Class 2 : H.264 video recording, MPEG-4, MPEG-2 video recording.
Class 4: MEPG-2 (HDTV) video recording, digital still camera (DSC) consecutive photo shooting.
Class 6: Mega-pixel DSC consecutive photo shooting, professional video camera.
Class 10: Full HD video recording, HD still picture consecutive shooting.

Can you save data in different formats such as audio, video, still pictures and documents on a single SD memory card?

Yes, you can save data in any format as long as the card has sufficient memory capacity. However, to play or transfer the data you will need a device that is compatible with the appropriate data format such as SD-Audio, SD-Video and SD Document.

What do you need to transfer data from a memory card to a computer?

Most computers are built with multiple ports for different data connection standards, including SD standards. If your computer is equipped with an SD slot, you can transfer data by simply inserting the SD memory card. If your computer does not have an SD slot, or is built to an earlier SD standard than your memory card, you can use a USB reader/writer or computer card adapter to transfer data from your memory card to your computer. Computer editing software for each type of data such as sound, music and still images also is needed.

What is the service life of an SD memory card?

This depends on how your product in manufactured. SD standards-based memory cards, like most semiconductor cards, store information in flash memory. The current technology along with normal usage typically gives the card a lifespan of 10 years or more, allowing consumers to upgrade their devices for many years and reduce consumer electronic waste.

Difference between SD and SDHC standard

The primary differences between an SD card and an SDHC card are maximum storage capacities and default file format. A standard SD card is manufactured in versions that store up to 2GB of data using FAT16 as the default format.

Some considerations on SD cards

An SDHC card is manufactured in versions that store from 4GB up to 32GB of data using FAT32 as the default format.

Both types of cards come in three different physical sizes: full SD, mini SD and micro SD.


SD standards are backward but not forward compatible. This means that a device that supports only the SD standard cannot read or write to an SDHC card, but a device designed for SDHC cards can read and write to an SD card. The SD extended capacity, or SDXC, standard supersedes SDHC. SDHC devices can't read or write to SDXC cards, but SDXC card readers can read and write to both SD and SDHC cards.


The SD card you use with a video recorder has to save data at least as fast as the recorder streams it. Higher video resolutions stream more data per second. SD cards have a speed class rating that defines how fast the card saves data.

SD and SDHC cards may have a speed class rating of 2, 4, 6 or 10, where 2 is slowest and 10 is fastest. Speed class 1, also called Ultra-High Speed is the fastest. UHS did not exist when the SD standard was created and is only available with SDHC and SDXC cards.

What is the SDXC standard?

The SDXC standard is the newest SD standard. It supports memory capacities above 32GB up to 2TB. Devices (cameras, video cameras, computers, etc.) that are compliant to the SD Physical Layer and File System 3.00 version specs can support SDXC memory cards as well as SDHC memory cards and SD memory cards.

Is the SDXC standard compatible with existing SD devices?

Existing SD devices and SDHC devices are not be compatible with new SDXC memory cards, but existing SD memory cards and SDHC memory cards will still continue to be offered by card manufacturers for the foreseeable future. Existing SD memory cards and SDHC memory cards will work in SDXC devices.

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