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Memory Cards: specifications, types


General type of memory card.

SD (Secure Digital). One of the most popular types of memory cards nowadays. They have a size of 32x44 mm and mechanical write protection — in the form of a slider. Support for SD cards is practically the standard for modern laptops and digital cameras, and such media are also very common in other devices (except for the most compact ones, where a smaller version is used — microSD ; it is described below). At the same time, we note that today this type includes three varieties:
  • Original SD standard. It supports up to 4 GB and relatively low speeds, which is why it is considered obsolete and rarely used. On the other hand, such cards can be used in almost all modern SD-card readers.
  • SDHC. An evolution of the original SD standard. The maximum capacity has been increased to 32 GB, and support for high-speed UHS bus (see "UHS Class") is possible, although this support is not required. SD HC cards can be used in card readers of this format, as well as in devices for newer SDXC.
  • SDXC. The newest SD card standard in common use today. Allows you to create media up to 2 TB; in addition, it was in this standard that the UHS bus was first introduced (after which it began to be used also in SDHC cards). In addition to card readers for this format, such media can also work with devices for SDHC — however, only if the card is formatted in the FAT32 file system, while by d...efault SDXC uses the exFAT system.
— microSD. A smaller version of the SD cards described above; the size of such a card is 15x11 mm. They are also very popular, but primarily in pocket technology — smartphones, tablets, portable players, etc. Like the full-size version, they have three varieties:
  • original microSD;
  • microSDHC;
  • microSDXC;
Application features are also similar: older cards can be used in newer card readers, but usually not vice versa.

— miniSD, miniSDHC. One of the smaller varieties of SD cards that preceded microSD (HC). Nowadays, it is considered completely obsolete and has practically fallen into disuse.

CompactFlash. One of the first memory card formats on the market. Includes two formats — CompactFlash Type I and CompactFlash Type II. They differ in read / write speed and size — Type II is faster and has a thickness of 5 mm (Type I — 3.3 mm with the same length and width of 42x36 mm). Due to this, a Type I card can be used with a Type II reader, but not vice versa. Despite its venerable age, this format is still popular in photographic equipment due to decent speeds and volumes (up to 128 GB); The main disadvantage is the large size compared to other formats.

CFast 2.0. High-performance drives for fast handling of large amounts of data. CFast 2.0 standard cards are the size of Compact Flash flash drives (42 x 36 mm), at the same time they have even more impressive read and write speeds (over 500 Mbps). Drives of this class excel when recording high-bitrate video in resolutions up to 8K, as well as in the genre of reportage photography with high-speed burst shooting in RAW. The amount of memory for CFast 2.0 flash drives can exceed 1 TB. Compatibility with memory cards of this standard is implemented in individual copies of top-end cameras and camcorders.

xD-Picture. A standard developed by Olympus and Fujifilm and used primarily in their digital cameras. The main feature of these cards is the lack of a memory controller — thanks to this they are reliable, compact (20x25 mm) and have low power consumption. On the other hand, the volume of such cards is low (up to 2 GB), the reading speed is also quite low, and they cost several times more than similar microSD media (including HC and XC). As a result, even the creators themselves are gradually shifting the focus towards other types of cards.

— memorystick. A proprietary standard developed by Sony specifically for its equipment back in 1998. It is closed, almost never used in devices from other manufacturers. It was widely used until the early 2010s, when Sony began to gradually move to the common SD standard. Nowadays, Memory Stick support is extremely rare, mainly in outdated devices.
Let's note that in this case cards of both the original form factor (50x21x2.8 mm) and Duo cards with reduced dimensions (31x20x1.6 mm) can be meant. The third size, micro, is placed in a separate paragraph (see below). However, all these form factors are compatible through the simplest adapters.

— Memory stick micro. The smallest version of the Memory Stick standard. For more information about this standard, see above, but here we note that Memory Stick micro (also known as M2) have dimensions of 15x12.5x1.2 mm.

— XQD. The successors of CompactFlash cards, developed by the CompactFlash Association specifically for devices that require high read and write speeds, in particular cameras and camcorders — the practical write speed reaches 125 Mb / s, and there is evidence that this is not the limit. At the same time, this card appeared relatively recently and is only gaining popularity. It has rather large dimensions — 39x30x4 mm, larger than SD, although it is somewhat inferior to CompactFlash.

— cfexpress. Incredibly fast high-capacity drives with an eye for long continuous recording in intensive mode. They are the best suited for shooting video in 4K resolution and higher with a frame rate of 120 fps. Advanced instances of the series provide write and read speeds of over 1 Gbps. Also, the cards of the line have resistance to damage during falls and high bending strength. There are two types of CFexpress drives: Type A with dimensions of 20x28x2.8 mm and Type B with dimensions of 38.5x29.8x3.8 mm.

— SxS. Memory card format jointly developed by Sony and SanDisk for professional video applications. It uses the PCI Express interface, which makes it possible to install such cards directly into the expansion card slot on a computer and laptop. It also has a high data transfer rate — up to 2.5 Gbps at the peak.

— PS Vita Card. A specialized memory card format designed, as the name suggests, for PlayStation Vita handheld game consoles. Created by Sony to replace UMD discs, not used by other manufacturers. It is proprietary, incompatible with universal standards like SD. Cards are available in capacities from 4GB to 64GB.

— Nano memory. A type of memory card introduced in 2018 by Huawei and mainly used in Huawei smartphones. Also known colloquially as nano SD, although this designation is technically incorrect. The size (area) of such a carrier is 45% smaller than that of popular microSD cards, while Nano Memory cards are identical in size and pin arrangement to nanoSIM SIM cards. This simplifies the use of combined slots in smartphones (suitable for both a SIM card and a memory card). As for the characteristics, initially for Nano Memory volumes up to 256 GB and read speeds up to 90 MB / s were announced; if this standard proves successful, these numbers can be expected to increase.


The nominal capacity of a memory card is the amount of data that can be written to it. For technical reasons, the real working volume of modern memory cards is usually somewhat less than the nominal one (for example, 14.9 GB with the claimed 16 GB). However, with the same type of card, differences in nominal capacity usually correspond to differences in actual capacity: for example, a 64 GB SDXC card will actually have twice the capacity of a 32 GB card of the same card.

Recall that different types of media have different limits on the maximum volume; see "Type" for details. And a specific volume is most often chosen by the manufacturer not arbitrarily, but from a list of standard options. The most widely used cards nowadays are 16 GB, 32 GB, 64 GB, 128 GB and 256 GB ; capacities of 8 GB or less are considered modest, with the most capacious models holding 512 GB or more.

Note that the price of the card directly depends on this parameter. Thus, many models are available in several variations, differing solely in capacity; and it is worth choosing by volume depending on the types of data that are planned to be stored on the card. Of the popular formats, text documents occupy the least space — usually tens, at most hundreds of kilobyte...s. The size of a photo from a modern camera or an MP3 file is already calculated in megabytes, music in lossless formats "weighs" already tens of megabytes, and the volume of a video depends on its duration, resolution and the codecs used.

Speed class

A characteristic that describes the minimum write speed to the card. It is given for SD and microSD cards (including their variations, see "Type") and is indicated by a number indicating the speed in MB / s: for example, class 10 corresponds to 10 MB / s.

Higher speeds provide more options, but come at a higher cost; in addition, it must be supported by the equipment where the card is used. So the choice for this parameter depends on the capabilities of such equipment and specific tasks. High speed is of key importance for video recording: for example, for video in Full HD (1920x1080) you need a card with a class of at least 4, and preferably 6 or even 10 (such characteristics already allow you to work with an increased frame rate).

Note that in the characteristics of many memory cards, you can see seemingly inconsistent figures. For example, a class 10 model can correspond to UHS Class 3 (which means the speed is no longer from 10, but from 30 MB / s) and the video recording class V60 (and this is already from 60 MB / s); and the overall write speed for it can be claimed at an even higher level — for example, 80 MB / s. All of these options are described in detail below; and here we note that there are no inconsistencies here. The fact is that the data regarding the UHS capabilities and the video recording class are relevant for operation via the UHS bus; if the card reader does not have such a bus, then the card's capabilities are limited by the gene...ral speed class. So, the model from our example in a card reader without UHS will be able to issue a maximum of 10 MB / s; and if you have UHS, it will work at least 60 MB / s, which does not contradict the requirements of UHS Class 3 (at least 30 MB / s). The overall write speed is usually indicated by the theoretical maximum, and in fact its value is often noticeably lower.

UHS class

UHS bus version supported by the memory card.

UHS is a communication technology used in SD/microSD cards of the (micro)SD HC and (micro)SD XC standards. It allows you to significantly increase the speed of data exchange compared to previous standards; at the same time, media supporting this technology is quite compatible with equipment that does not have UHS — except that speeds in such cases will be limited by the capabilities of the card reader, and not by the card itself.

As for versions, their names consist of two parts: UHS generation (I or II) and class (1 or 3) — for example, UHS-I Class 1. Actually, this is the most modest version of UHS found in modern memory cards; in addition to it, UHS-I Class 3 and UHS-II Class 3 are popular. The UHS generation determines the maximum data transfer rate (usually meaning read mode) — it is 104 MB / s for version I and 312 MB / s for version 2. “Class”, in turn, determines the lowest (guaranteed) write speed : it is at least 10 MB / s for Class 1 and at least 30 MB / s for Class 3. Different versions of UHS are quite compatible with each other, except that the speed in such cases will be limited by a slower standard.

Note that for UHS cards, other paragraphs may also indicate more advanced characteristics — for example, the video recording class (see below) V90 for a UHS-II Class 3 card. There are no contra...dictions here: the speed of 90 MB / s provided by such a card in write mode, fully satisfies the “at least 30 MB / s” condition provided for UHS Class 3.

Video recording class

The video recording class supported by the memory card.

This parameter is specified for SD/microSD cards and their variations, as well as CompactFlash (see "Type"). In the first case, the V* format designation is used, in the second, VPG*, but the idea is the same there and there: the numbers indicated instead of an asterisk are the lowest write speed (in MB / s) that the card is guaranteed to provide. This speed is of key importance primarily in video shooting, which is why this parameter is called “Video Recording Class”; the higher it is, the higher the resolution and frame rate at which you can record using this card.

The minimum video recording class found in modern cards of the SD / microSD family is V6, it already allows you to work with HD and Full HD video. However, for Full HD it is desirable to have a card of at least V10 level. And the V30 class already allows you to comfortably work with Ultra HD 4K. Faster cards are also being released — V60 and even V90, suitable already for 8K resolutions and higher.

In turn, in CompactFlash cards you can find models of classes VPG20, VPG65 and VPG130

Note that the video recording class may well be higher than the general speed class and/or UHS class (see above). However, there are no contradi...ctions here. The requirements for the UHS class provide a write speed "not lower than ..."; thus, for example, all cards with a video recording class of V30 and higher will comply with the UHS Class 3 standard (“at least 30 MB / s”). And the general speed class describes the card's capabilities when working with equipment without UHS support (and such equipment is practically not used in video recording).

Application class

The application speed class that the memory card corresponds to.

When working with applications that use a memory card (for example, mobile games), information is written and read not in a continuous stream, as when recording video or copying data, but in separate small fragments, moreover, from random sections in the memory of the drive (the so-called random write / read). So a high video recording class (see above) does not always mean good performance when working with demanding games and other resource-intensive programs. Therefore, in the characteristics of memory cards, they began to separately indicate the speed class for applications.

The key indicator for assigning one or another class is the minimum number of IOPS (input / output operations per second) that the media can provide in random write and read mode. The following classes are relevant today:

A1 — at least 1500 IOPS for reading and 500 IOPS for writing;

A2 — at least 4000 IOPS and 2000 IOPS, respectively.

The speed of continuous recording (for example, when shooting video) in both cases must be at least 10 MB / s (often it turns out to be even more — see “Speed class”, “Video recording class”).

In the future, we can expect the appearance of new, more performant classes for applications. Also note that this parameter significantly affects the price of the card.

Speed value

Factor describing the maximum speed of the card in read mode. In this case, 150 KB / s is taken as a unit; thus, for example, a speed value of 533x corresponds to 150 * 533=79,950 KB / s, that is, about 80 MB / s.

In general, this parameter is quite specific; in fact, it is easier to focus on the directly claimed reading speed (see below). However, sometimes it is not indicated — in such cases, the speed value will be primarily useful.

Read speed

The maximum speed of reading data from a memory card.

Any modern memory card provides sufficient reading speed for simple everyday tasks — like copying photos from a camera to a laptop. Therefore, it makes sense to pay attention to this parameter mainly in cases where the card is purchased for professional use, or if high speed is critical for you — for example, if you often have to copy photos from the camera in a hurry. In doing so, two points should be taken into account. Firstly, the corresponding speed must be supported by the card reader where the card is used. Secondly, this paragraph indicates the theoretical maximum — in perfect conditions; the actual reading speed may be lower (if we are talking about cards with UHS, this speed can be estimated by the UHS class, see above about it). Nevertheless, it is quite possible to compare different models of cards by this indicator: differences in theoretical speed usually quite correspond to the difference in actual speed.

Write speed

The maximum speed for writing data to a memory card.

High write speed is important for tasks that involve storing large amounts of data in a limited amount of time. However, note that this paragraph indicates the theoretical maximum speed for perfect conditions; in fact, this value can be noticeably lower. Therefore, the characteristics of memory cards also indicate the minimum guaranteed write speeds in different modes — the general speed class, the UHS class, the video recording class and/or the class for applications. All of them are described in more detail above. However, you can also evaluate the capabilities of the carrier by the overall speed: other things being equal, a card with a higher theoretical speed will work faster in fact.

As for specific values, speeds from 4 MB / s and from 6 MB / s are practically not found nowadays, from 10 MB / s and from 16 MB / s can be called average indicators, from 50 MB / s — above average, and the fastest models have a maximum write speed of 100 Mbps or more.

Increased reliability (loop recording)

Memory cards with high reliability design. Among other things, this increases the service life — in other words, such a medium is able to endure more rewriting cycles than a regular one. Such durability is achieved, in particular, through the use of special controllers that ensure the most even distribution of the load over the memory cells.

Endurance memory cards are positioned primarily as the best choice for video cameras operating in adverse conditions — video recorders (including motorcycle and bicycle), action cameras, outdoor surveillance cameras, etc. In such video equipment, the so-called cyclic shooting mode is often used: when the drive is full, new material starts to automatically overwrite the oldest, which allows you to avoid interruptions in recording. This type of memory card, due to its increased durability, is great for working in this mode. In addition, media marked with Endurance usually also have an increased degree of overall protection — from dust, moisture, temperature extremes, shock / shock, and even X-rays. This increases the likelihood that the contents of the card will remain intact even in the event of an accident or other emergency.


Wi-Fi wireless module built right into the memory card. Such a card is actually not only a storage device, but also a Wi-Fi adapter, allowing the corresponding device to connect to the network. Most often, this feature is used in digital cameras in the form of Eye-Fi technology: by inserting an Eye-Fi card into the camera, you can transfer footage from it to a computer and even send it directly to the Internet without wasting time and effort on a wired connection. At the same time, the technology allows you to do all this right in the process of shooting, and copies of images can be stored on the card or deleted after sending to ensure free space. Special software for working with Wi-Fi is most often supplied on the card itself. It should be noted that such cards can fully work only in devices that support this technology; a regular card reader will "see" only the memory of the drive, while the Wi-Fi module will not be available.

Write protection

The ability to put the card in read-only mode, which allows you to protect important data from accidental overwriting or erasure. It is usually implemented as a mechanical switch-slider, the position of which determines the operating mode of the card. It should be taken into account, however, that this slider is just an indicator signaling the card reader about the selected mode, and its position does not affect the card itself in any way; in some card readers, the write protection function may simply be absent — such devices will not “see” the position of the slider.

2x set

A set that includes two cards with the same characteristics at once.

These kits come in handy for a variety of situations. The most typical example is working with a camera that has two slots for memory cards (such functionality is quite popular among advanced cameras), but other applications are possible — for example, you can keep the second card with you just as a spare. Anyway, buying a paired set is more convenient, and often even more profitable, than buying two cards separately.

Adapter included

An additional adapter is included with the memory card.

The adapter is a device with which the card can be installed in a non-native format card reader. Nowadays, microSD cards are mainly equipped with such a device — adapters are designed to install such media in a slot for a full-size SD card. This is convenient primarily for exchanging data between portable gadgets like a smartphone / tablet and larger equipment like PCs and laptops — for example, to copy pictures from a smartphone camera to a computer or music from a computer to a smartphone.

Card reader included

The presence of its own card reader in the delivery set of the card.

Such a card reader is usually a miniature memory card reader connected to a computer via a USB port. When installed in such a device, the card actually turns into a USB flash drive and can be used even on those computers where there are no card readers — a free USB connector is enough.

Manufacturer's warranty

Manufacturer's warranty provided for this model.

In fact, this is the minimum service life promised by the manufacturer, subject to the rules of operation. Most often, the actual service life of the device is much longer than the guaranteed one. But an indicator of 5 years suggests that the memory card is more likely to be lost or become irrelevant. You can also come across a lifetime warranty, but in this case it is better to clarify the details of what it applies to. And anyway, it implies a certain period of time, though measured in decades. In addition to confirmation of reliability, such a guarantee allows you to contact the supplier after a while to eliminate possible problems (of course, not mechanical). But the difficulties in implementing this procedure (the representative office is located only in large cities) and the rare cases of the need for this (after all, it is easier to buy a new flash drive, with the exception of vital information on the old media) make the lifetime warranty more of a marketing ploy than a cool chip.
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