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Summary

SD card is familiar to every one since it has been used in many aspects, such as in your smart phones, cameras and video games. This essay will cover about SD card speeds, classes, specifications, capacities and service life. By the way, we will tell you how to buy an appropriate SD card.



how about sd card speeds

Part 1: Catagory and Development of Mini Storage Card

Mini mobile storage cards have been developed into many classes in a long time. These SD cards are corresponding to different devices. Here are some common data storage cards:
① CF card
CF card, or Compact Flash memory card for short, was manufactured in 1994 by SanDisk, and then improved by Hitachi, Toshiba, Ingentix and Matsushita, which is the longest-lasting storage card in the current market. With the flash memory technology implemented, CF card is a stable solution to data storage, free from battery-powered supply, outperforming the previous cards (i.e. PC card) in security and protectiveness. It is primarily designed for digital cameras. Compared with PC (PCMCIA), it looks smaller but runs faster. Now, CF card is still the standard for some high-level professional digital cameras. Yet, the capacity limitation lags it behind the growing pixels of digital cameras. It also cannot be performed in many places because it is larger than the other kinds of storage cards and it merely works between 0 – 40℃.

comact flash card

②  MMC
MMC (Multi-media Card) was unveiled in 1997 by Siemens AG and SanDisk. The standard size of MMC is 24mm*32mm*1.4mm. Originally, it targeted at phones and pagers. But its size is soon accepted in many applications, such as digital cameras, PADs, MP3 players, laptops, portable video game consoles, digital video cameras and portable GPSs.

multi media card

③ SD Card
At first, MMC allowed for pirated music, which challenged the digital rights management in the music industry. Therefore, in 1999, Matsushita, Toshiba and SanDisk added encryption hardware on MMC and co-introduced the new card – SD (Secure Digital) card. Compared with MMC, it is 0.7mm thicker than MMC while compatible with the SDMI digital rights management, with the highly dense storage capacity. However, MMC can be inserted into the standard SD card slot but SD card cannot into the MMC slot.
Note: SD card mentioned above refers to the standard SD card. As the time goes on, it derives Mini SD card and Micro SD card.
sandisk sdxc card
④ TF (micro  SD)
TF card, also called as T-Flash card or Micro SD card, is the abbreviation of TransFlash. Co-developed by Motorola and SanDisk in 2004, it is the subminiature card (11mm*15mm*1mm), about a quarter of the standard SD card. That should be the smallest storage card at present. It was mainly designed for shooting large images and downloading large video clips in camera phones. Now, it is used as data storage media. transflash or mirco sd card

Part 2: Classes, Applications and Speed of SD Card

SD card is the new generation type upon the semi-conductor flash memory. Many products are derived the standard SD card as the technology of SD card is growing. These SD cards that differ from capacities and sizes are suitable in various devices, detailed as below:
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1. SD Card Classes

① There are three sizes of SD card in general use: SD card, Mini SD card and Micro SD card. Standard SD card is in full size. They are used in most of DSLR cameras and video cameras. It is noticed that it only has three corners, with one missed at the top. Mini SD card is smaller than standard SD card, but it is rather similar with the standard SD card in performance. Mini SD card is small, stable, and completely compatible with the standard SD card slot as it is used with the specific adapter. In addition, Mini SD card is designed to be in low power consumption, so it is more suitable for mobile telecommunication devices, like mobile phones and PDAs. Micro SD card, originally named as Trans-flash Card (TF card for short), was officially called as Micro SD card in 2004. It is produced by SanDisk, mainly used in mobile phones.

different sd card sizes and types

(From left to right: SD card, Mini SD card and Micro SD card)

② Each class of card has a memory capacity range, namely SD, SDHC (SD High Capacity) and SDXC (SD Extended Capacity). SDHC and SDXC are mainly sold in the current SD card market while the SD standard is gradually phased out by the market due to the low capacity. comparison between sd mini sd and micro sd card
Note: FAT16 and FAT32 file systems are supported in Windows and MacOS; exFAT can be supported in Windows 7, Windows 8, MacOS X10.6.6 and the above versions.

2. SD Card Applications

SD card is mainly used in:
  • Digital cameras to save photos and videos;
  • Digital video cameras to save photos and videos;
  • PADs to save various data;
  • Mobile phones to save photos, ringtones, music and videos;
  • Multi-media players, like MP4 and home theatre;
  • Portable game consoles, like Nintendo 3DS, NDS and NDSL.

3. SD Card Speed

Each SD card transmits data at different speed. The SD Association classifies the speed ratings corresponding to the minimum read speed in MB/s. It defines 3 speed standards: Speed Class, UHS Speed Class and Video Speed Class, shown as below:
Mini. Sequential Write SpeedSpeed ClassUHS Speed ClassVideo Speed ClassSupport 4K video
2MB/Sclass 2 of sd card speed Class 2 (C2)————×
4MB/Sclass 4 of sd card speed Class 4 (C4)————×
6MB/Sclass 6 of sd card speed Class 6 (C6)——video speed class 6 Class (V6)×
10MB/Sclass 10 of sd card speed Class 10 (C10)uhs speed class 1  UHS-1video speed class 10 Class (V10)×
30MB/S——uhs speed 3 UHS-3video speed class 30 Class (V30)
60MB/S————video speed calss 60 Class (V60)
90MB/S————video speed class 90 Class (V90)

Speed Class

From the SD 2.0 specification, the Speed Classes defined by the SD Association are Class2, 4, 6 and 10.

UHS Speed Class

UHS (Ultra High Speed) is the SD card bus standard for SDXC. UHS Speed Class is applicable to both SDHC and SDXC. The UHS Speed Classes defined by the SD Association are UHS Speed Class 1 (UHS-1) and UHS Speed Class 3 (UHS-3). U1 and U3 can be applied to UHS Bus IF product series(UHS-I, UHS-II & UHS-III). We can learn about the information from the symbols marked on the SD card.

Video Speed Class

Video Speed Class is defined to answer a demand for high resolution and high quality 4K/8K video recording and it also has an important feature to support next generation flash memory such as 3D NAND. Furthermore, it covers speed of HD (2K) video. The Video Speed Classes defined by the SD Association are V6, 10, 30, 60 and 90. V6 and V10 can be applied to High Speed and UHS Bus IF product series. V30 can be applied to UHS Bus IF product series. V60 and V90 can be applied to UHS-II / UHS-III product series. Take video cameras as an example. If you don’t figure out whether the video speed of the SD card suites the video camera, you should view the instruction where the supplier will illustrates the best speed rating.

4. NAND Cells and Lifespan of SD Card

① NAND cells
Memory chip and controller chip, two SD card components, are crucial indicators in performance. The physical specification of each SD card is identical but the chip may not. The chips used in the SD card can affect how long it can work and how fast it can read/write. We should know that the storage area only account for 1/3 of a SD card. NAND cells are the memories that make the SD card store all data. According to the number of NAND cells, NAND Flash types can be divided into SLC (Single Level Cell), MLC (Multiple Level Cell), TLC (Triple Level Cell) and QLC (Quad Level Cell). Of course, their life spans and prices are different.
  • SLC (Single Level Cell): The SLC flash memory contains a single bit in each cell. The process that It writes data causes little voltage change. It has long lifespan, about 100,000 erase cycles. Yet the cost is higher 3 times than that of MLC so it is generally used in some high-end business products.
  • MLC (Multiple Level Cell): The MLC flash memory contains two voltage thresholds, with two bits in each cell. It has long lifespan, about 3,000 to 10,000 erase cycles. It is generally used in high-end daily products.
  • TLC (Triple Level Cell): The TLC flash memory, as the extension of MLC, reaches 3 bits of information per cell. Compared with MLC, it has more storage capacity, higher storage density and lower price, more than 1.5 times the capacity of MLC. Yet, it reads/writes not quickly and the read/write cycles are about 1,000 to 2,000. Currently, it is welcomed by the SD card manufacturers.
  • QLC (Quad Level Cell): The QLC flash memory can store 4 bits per cell. Compared with TLC, QLC store more 33% data than TLC. Besides, the program/erase cycles can reach 1,000 times, equal and even better than that of TLC. It is also cheaper than TLC.
All in all, in terms of performance, durability and price: SLC > MLC > TLC > QLC.
② Service life of SD card
The lifespan of SD card is limited, especially that of the TLC or QLC SD cards are shorter. If you wonder how long the SD card can be used, you can estimate the erase times, or judge from the warranty period of the SD card. Generally, each SD card manufacturer provides the quality warranty service. Few problems will happen in this period. Yet, you should pay attention to the data security and storage once it is beyond this period. In other words, the warranty period is the lifespan. Warranty periods of main branded SD cards:
ProductWarranty period
SanDisk SD/SDHC/SDXC storage cardWithin 5 years since the date of purchase
Kingston SD/SDHC/SDXC storage cardLifetime warranty
Lexar SD/SDHC/SDXC storage cardWithin 2 years since the date of purchase
Toshiba SD/SDHC/SDXC storage cardWithin 5 years since the date of purchase
Besides, the SD card without wear leveling will be shortened the lifetime. Wear leveling attempts to balance each block by arranging data that erasures and rewrites are distributed evenly across the medium. In this way, no single block prematurely fails due to a high concentration of write cycles. Otherwise, the flash memory without this technology can repeatedly writes data on the identical blocks. These blocks will soon be excessively worn out, along with more chances of its corruption. wear leveling explanation
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Some people notice that there are many SD card types, SDHC, SDXC and even XQD. So, what is different between these types?

Part 3: What is Different between XQD, SDHC and SDXC

XQD is a memory card format developed for flash memory. The format was announced in 2010 by SanDisk, Sony and Nikon. Taking PCI Express as a data transfer interface, it offers writing speed at 125MB/s. Now, although the XQD card can read data up to 440MB/s and write at 400MB/s, it hasn’t been widely used yet. The main storage mediums of cameras are still SDHC and SDXC. While XQD cards are served for professional DSLR cameras. Differences between XQD, SDHC and SDXC:
XQD cardSDHC cardSDXC card
Imagexqd sd cardSD Cardsandisk sdxc card
Release date201020062009
Specification38.5*29.8*38mm24*32*1.4mm24*32*1.4mm
Capacities32GB, 64GB, 128GB, 256GB2GB, 4GB, 8GB, 16GB, 32GB32GB, 48GB, 64GB, 128GB, 256GB, 512GB, 1TB, 2TB
ManufacturerSony, Nikon, Lexar (quitted)SanDisk, Kingston, LexarSanDisk, Kingston, Lexar
File systemRAW image, MOV, 4K XAVC-S video fileFAT32 by default; support RAW, JPEG image and streamline to record and play 2k/4k videosexFAT by default; support RAW, JPEG image and streamline to record and play 2K/4K videos

Part 4: Why SD Card is Easily to Get Damaged

Although the SD card improves our life a lot, it also has inevitable demerits.
Merits: ● Wide applicability — Everyone can easily pick up the suitable card for their portable devices due to various sizes and capacities. ● High security — Encryption built in the SD card can ensure the data security. It is also designed with CPRM (Content Protection Recordable Media), the technology used to protect the copyrights in DVD.

Demerits: ● Vulnerability — The small size makes the SD card to be easily gotten physically damaged and snapped. The improper using ways also shorten the lifespan.

When you cannot delete the files on the SD card, or you are prompted to format the SD card, the card has already been damaged. But, why it gets damaged? The followings are reasons:

1. Physical damage

The tiny SD card easily gets physical damages, such as being snapped and being soaked. Besides, electrostatic discharge on the components is also an inducement to the damage.

2. File system damage

The operation systems can affect the SD card. We basically get access to the data on the SD card through the operating system of camera/phone. If the faulty system can damage the file system, the SD card will be damage and inaccessible.

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3. Bad sectors in SD card

Like the traditional hard disk, bad sectors inevitably happen in the SD card. Bad sector in computing refers to a storage unit that is permanently damaged. Once these sectors pile up to the upper limit, the SD card cannot be used any more.

4. Plug in/out SD card improperly

The SD card will be damaged if plugged in/out improperly. If the SD card is suddenly stopped and plugged out when reading/writing data, or it is frequently inserted into various devices, the card will be damaged soon.

5. Virus/malware attack

This reason cannot be dismissed. If you accidentally download malware to your smart phone, it can be placed in the SD card. Then, the SD card may be attacked to be unreadable and inaccessible.

6. Break-off in formatting

The fact that the formatting process is broken off will hurt the SD card, which is really hard to fix. Be cautious when you are going to format the SD card.

7. No wear leveling

Given the production cost, wear leveling isn’t set in the SD card. Data will be repeatedly erased and written on the same blocks of the card, which will turn them into bad sectors. Gradually, the card will fail to read or write due to these permanently bad sectors.

8. Manufacturing defects

The price is always telling you the truth. Some SD cards are not qualified. The cheaper SD card may contain more manufacturing defects and get more damages easily. So, select a well-quality SD card.

Once the SD card is damaged, all data may be lost, deleted or formatted. Don’t worry! Renee Undeleter can bring them back. Besides, if your SD card cannot be read in Android phones and cameras, link to Digital camera can not read SD card and Android phone can not read SD card for more!
Of course, in case of troubles, we should pick up the high-quality, high cost-effective SD card for us. Facing with so many SD cards, how to select a SD card?

Part 5: How to Select SD Card

Brand, type, size, quality, all of them are factors that you should consider when purchasing a SD card. No matter which device you are using, mobile phone, tablet, video camera, digital camera or the other electronic devices, you can follow these ways to select a SD card.

1. Type and brand

First, check whether the SD card is compatible with your device. See if there is the SD logo or the other certification logos on the device. Then, refer to the device instruction and check which types of SD card can be used in it. If the device suites the SDXC standard, SD, SDHC and SDXC card can be used. SD and SDHC card can be used in the SDHC device. SD device can only accept SD card. At present, Lexar and SanDisk are main SD card suppliers. Besides, Kingston, Transcend, Toshiba and Samsung are famous brands with relatively cheaper SD card than the former ones. Don’t buy the card on the informal platforms or malls. Or, you may buy a fake or refurbished SD card.

2. Size

Three sizes: standard, mini and micro. Select the one that suites the slot completely. Now, Micro SD card is used in smart phone; standard SD card in laptops, video camera, digital camera and the other portable devices; Mini SD is seldom used. The SD card slot and the instruction will give you this answer.

TipsCard reader is a useful tool. Through this tool, Micro SD card can be inserted into the slot of Mini or standard SD card; Mini SD card can be used in the slot of standard SD card. So, you can prepare a card reader for you Micro SD card.
insert micro sd card into card adapter
3. Capactiy

As for capacity, you should consider the maximum capacity available in the device but also your daily needs. If you are a photography fan, which format would you prefer to, RAW or JPEG? How many image pixels do you like? The size of a RAW photo with 2,400 pixels is around 40MB. Some high-resolution cameras, like Sony A7R3, Nikon D850 and Cannon 5DS, are able to produce 4K photos. 64GB SDXC cards should be used in these high-pixel images. All in all, if you want to shoot 4K videos, 64G SDXC is elementary. If you only like taking JPEG photos, 32GB is totally enough.

Capacities of each SD card type:

TypeCapacity
SD card8MB/16MB/32MB/64MB/128MB/256MB/512MB/1GB/2GB
SDHC card2GB/4GB/8GB/16GB/32GB
SDXC card32GB/48GB/64GB/128GB/256GB/512GB/1TB/2TB
The capacity is marked on the SD card. This table is for your reference only.
4. SD card speed

Speed rating is the minimum data transfer speed of a SD card, also the minimum writing speed. The speed rating symbol is marked on the SD card. These symbols are defined by the SD Association. See as below:

how sd card speed shown on the product

You can select one based on your device and your needs:

Mini. Transfer speedSymbolUse
2MB/sclass 2 of sd card speedSave file, record standard HD videos
4MB/sclass 4 of sd card speedSave file, record standard HD videos
6MB/sclass 6 of sd card speedSave file, record standard HD videos
10MB/sclass 10 of sd card speedRecord full HD (1080p) videos and capture HD static images
10MB/suhs speed class 1Record 1080p videos in large size, capture HDTV programs
30MB/suhs speed 3Record 1080P/4K videos in large size, capture HDTV programs at 60/120FPS
6MB/svideo speed class 6Record 720p to 1080p videos
10MB/svideo speed class 10Record full HD videos and 1080p live
30MB/svideo speed class 30Record 1080p and 4K videos at 60/120 fps
60MB/svideo speed calss 60Record 8K videos at 60/120 fps
90MB/svideo speed class 90Record 8K videos at 60/120 fps
Speed rating affects the price a lot. You don’t need to emphasize on the speed too much. Besides, recording video requires a constant minimum write speed to avoid ‘frame drop’ during recording for a smooth playback. That means the write speed cannot be too fast or too slow. Even though the SD card can write data faster, it is unable to perform in a not excellent device. Therefore, reading the device instruction to find the suitable card is a better choice. Generally, if you are going to record a HD video, you need a Class 4 card, at least. Class 2 card are commonly used in the standard HD videos or to back up/transfer files.
Tips To buy a suitable SD card, pease check whether the device can support the SD card, including speed rating, size and capacity. Make sure the read/write speed and the capacity is practical to your daily use.