SD cards are a popular type of flash-based storage media commonly used in cameras, mobile phones, tablets, and other electronic devices. SD stands for “Secure Digital.” The most recognizable feature of SD cards is the logo, which depicts a circle with a cutout corner.
The official SD logo signifies that the card meets the standards set by the SD Association for capacity, performance, and interoperability. While the logo has evolved over the years, the cutout corner has remained since the format was first introduced in 1999.
This article will provide an overview of SD cards, explain the meaning behind the logo, and discuss the types, speed classes, and capacities available.
History of SD Cards
SD cards were first introduced in August 1999 by SanDisk, Panasonic (Matsushita Electric), and Toshiba as an advancement over MultiMediaCards (MMC). The SD card was designed to overcome the storage limitations of MMCs and provide greater capacity and speed for recording high-quality images and video. At the time, flash-based storage cards were still relatively new, and SD cards offered a major leap forward in performance compared to prior options.
The creators of SD cards aimed to provide a physically smaller, higher capacity storage solution capable of holding full-resolution images and high-bitrate video. Early SD cards started at 8 MB and quickly grew to offer capacities up to 2 GB over the next several years. The SD format has continued evolving since then, with SDHC and SDXC pushing capacities to 32 GB and higher while boosting performance through speed classes.
Description of the SD Logo
The iconic SD logo features a stylized depiction of an SD card with cut corners. The shape represents the physical design of SD cards, which have a notch or chamfer on one corner to help users orient the card correctly when inserting into devices.
The SD logo uses the colors blue, white, and gold. The blue represents the semiconductor silicon material used in memory chips. White symbolizes the purity and precision of digital technology. Gold represents the value and performance of SD cards.
Together, the SD logo’s distinct shape, colors, and letters visually communicate SD technology in a simple and memorable graphic. The logo appears on all authentic SD cards as a guarantee of compatibility and reliability. This gives users confidence they are getting a genuine SD card that will work as expected in devices.
According to the SD Association which oversees SD standards, the logo signifies that SD cards comply with standardized specifications. This ensures cross-platform performance and interoperability. The SD mark guarantees users a certain level of speed, quality, and capabilities.
Types of SD Cards
There are three main types of SD cards: SD, miniSD, and microSD.
SD cards were the original format introduced in 1999 by SanDisk, Panasonic and Toshiba, with capacities up to 2GB. They are larger than other SD card types with dimensions of 32mm x 24mm x 2.1mm.
miniSD cards were introduced in 2003 as a smaller alternative to SD cards, with dimensions of 21.5mm x 20mm x 1.4mm. Capacities range from 16MB to 2GB. A miniSD card comes with an adapter to allow its use in an SD card slot.
microSD cards were introduced in 2005, designed for use in mobile phones and other small devices. They are the smallest SD card format with dimensions of 15mm x 11mm x 1mm. microSD capacities range from 16MB to 2TB with high speed transfer rates.[1]
Speed Classes
SD cards have speed classes that indicate their minimum write speeds. Faster write speeds allow recording higher resolution videos and working with larger files quickly. The main speed classes are:
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Class 2 – Minimum write speed of 2 MB/s
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Class 4 – Minimum write speed of 4 MB/s
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Class 6 – Minimum write speed of 6 MB/s
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Class 10 – Minimum write speed of 10 MB/s
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UHS Speed Class 1 (U1) – Minimum write speed of 10 MB/s
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UHS Speed Class 3 (U3) – Minimum write speed of 30 MB/s
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Video Speed Class V6, V10, V30, V60, V90 – Minimum sequential write speeds for video recording
Higher speed classes allow for faster transfer speeds and support more intensive tasks like 4K video recording. Most modern SD cards are Class 10 or UHS Class 1 or 3. Checking for these speed classes can ensure your card can handle your device’s demands.
Capacity
SD cards come in different storage capacities, ranging from small to very large. According to the SD Association, there are several defined capacity ranges (SD/SDHC/SDXC/SDUC):
- SD cards: Up to 2GB
- SDHC: More than 2GB up to 32GB
- SDXC: More than 32GB up to 2TB
- SDUC: More than 2TB up to 128TB
The capacity determines how much data you can store on the card. Lower capacity cards are good for smaller amounts of data like photos, while high capacity cards allow you to store more photos/videos, large files, or even entire operating systems.
Capacity has increased dramatically over the years. Early SD cards were just a few megabytes, while today’s largest SDXC cards can store up to 2 terabytes of data. This allows people to store vast libraries of photos/videos and large files comfortably on a tiny SD card.
Uses of SD Cards
SD cards are most commonly used for portable storage in consumer electronics devices such as digital cameras, camcorders, smartphones, tablets, handheld video game consoles, and portable media players (Lenovo). This allows people to expand the storage capacity of their devices to store more data like photos, videos, music, apps, and other files.
Some specific uses and devices SD cards are commonly used in include:
- Digital cameras and camcorders to store photos and videos (MakeUseOf)
- Smartphones and tablets to increase storage for apps, media files, and more
- Handheld gaming devices like Nintendo Switch to download games and save game data
- Dash cams and security cameras to record and save footage
- Drone cameras to store aerial photos and videos captured
- Audio recorders to save recordings
- GPS navigation devices to store map data
SD cards provide removable, reusable, portable storage that can easily expand capacity when built-in storage is limited. Their compatibility across consumer devices makes them universally useful for storing and transferring data.
Advantages of SD Cards
SD cards provide many benefits that make them a popular storage option. Some key advantages include:
Increased storage capacity – SD cards allow you to add substantial storage space to your device like a smartphone or camera. This provides more room for photos, videos, apps and other files.
Cost-effective – SD cards offer an affordable way to add storage. The cost per gigabyte is low compared to built-in storage options.
Portability – The small size and removable design of SD cards makes them extremely portable. You can easily transfer files between devices.
Durability – With no moving parts, SD cards can withstand shock, vibrations, heat, and other harsh conditions.
Compatibility – SD cards are universally compatible with many devices including cameras, smartphones, tablets, drones, game consoles and more.
Speed – SD card speed classes allow you to choose a card that meets your performance needs depending on usage.
As you can see, SD cards offer significant advantages for conveniently expanding storage in a portable and affordable way. Their durability and universal compatibility also make them very practical and useful.
Disadvantages
While SD cards offer a number of benefits, there are some drawbacks to consider as well. Some disadvantages of using SD cards include:
Speed – SD cards are generally slower than internal storage, which can lead to slower app launch times and lagging performance, especially for demanding apps and games (Source). The speed class of the SD card impacts performance.
Failure Risk – Like any storage media, SD cards can fail or become corrupted over time, leading to potential data loss. This risk may be higher compared to internal storage (Source).
Difficult Organization – With apps split between internal storage and SD card, managing files and docs can become disorganized (Source).
Not All Apps Supported – Some apps don’t allow moving to external SD storage, limiting flexibility (Source).
The Future
Going forward, SD card technology will likely continue to evolve by improving speed and storage capacity. According to the SD Association, the new SD Express standard will enable speeds up to 985 MB/s and capacities up to 128TB, which camera manufacturers may start adopting in 2021.
The microSD format is also expected to see improvements, with forthcoming microSD Express cards that can deliver SSD-like performance. Industry analysis predicts the global microSD market will see steady growth of 2.2% CAGR through 2027, indicating these cards will continue playing a major role in consumer electronics.
Further into the future, holographic storage is being researched as the next potential leap in capacity and speed. However, this technology remains expensive and challenging to commercialize. For now, incremental improvements to NAND flash storage seem the most likely path for SD cards over the next 5-10 years.