Type
General type of memory card.
—
SD (Secure Digital). One of the most popular types of memory cards today. They measure 32x44 mm and have mechanical write protection in the form of a slider. Support for SD cards is almost a standard for modern laptops and digital cameras, and these media are also quite common in other devices (except for the most compact ones, where a reduced variety is used —
microSD; it is described below). Note that today this type includes the following varieties:
- SDHC. Evolution of the outdated original SD standard. Maximum capacity increased to 32 GB, support for UHS speed bus is possible (see “UHS Class”), although such support is not mandatory. SDHC cards can be used in card readers of this format, as well as in devices for newer SDXC.
- SDXC. The newest SD card standard among the widely-used today. Allows for the creation of storage up to 2 TB; furthermore, it was in this standard that the UHS bus was first introduced (after which it was also applied to SDHC cards). In addition to card readers for this format, these media can also work with devices for SDHC — but only if the card is formatted in the FAT32 file system, while by default SDXC uses the exFAT system.
— microSD. A reduced 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 varieties — 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 reduced varieties of SD cards, preceding microSD(HC). Nowadays it is considered finally outdated and has almost fallen out of use.
— CompactFlash. One of the first formats of memory cards on the market. Includes two formats — CompactFlash Type I and CompactFlash Type II. They differ in reading/writing speed and sizes — Type II works 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 reader for Type II, but not vice versa. Despite its venerable age, this format is still popular in photo equipment due to decent working speeds and capacities (up to 128 GB); the main drawback is large sizes compared to other formats.
— CFast 2.0. High-performance drives for fast operation with large data arrays. CFast 2.0 standard cards have the size of Compact Flash drives (42 x 36 mm), while boasting even more impressive reading and writing speeds (over 500 MB/s). This class of drives excels in recording video with high bitrates up to 8K resolution, as well as in reportage photography with high-speed continuous shooting in RAW. The memory capacity of CFast 2.0 drives can exceed 1 TB. Compatibility with memory cards of this standard is implemented in certain high-end cameras and camcorders.
— xD-Picture. A standard developed by Olympus and Fujifilm, mainly used in digital cameras of these companies. The main feature of these cards is the absence of a memory controller — thanks to this, they are reliable, compact (20x25 mm), and have low power consumption. On the other hand, the capacity of such cards is low (up to 2 GB), the reading speed is also quite low, and they are several times more expensive than similar media of the microSD format (including HC and XC). As a result, even the creators themselves are gradually shifting the emphasis towards other types of cards.
— MemoryStick. A proprietary standard developed by Sony specifically for its equipment back in 1998. It is closed and was almost never used in devices from other manufacturers. It was widely used until the early 2010s, when Sony began to gradually switch to the widespread SD standard. Nowadays, support for Memory Stick is extremely rare, mainly in outdated devices.
It should be noted that in this case, both original form-factor cards (50x21x2.8 mm) and Duo cards, which have reduced sizes (31x20x1.6 mm), can be implied. The third size, micro, is listed as a separate item (see below). However, all these form-factors are compatible through simple adapters.
— MemoryStick micro. The most miniature version of memory cards in the Memory Stick standard. For more details about this standard, see above; here, note that Memory Stick micro (also known as M2) has dimensions of 15x12.5x1.2 mm.
— XQD. Successors to CompactFlash cards, developed by the CompactFlash Association specifically for devices requiring high reading and writing speeds, particularly photo and video cameras — with practical writing speed reaching 125 MB/s, and there is evidence to suggest this is not the limit. At the same time, this card appeared relatively recently and is still gaining popularity. It has fairly large dimensions — 39x30x4 mm, larger than SD, although somewhat smaller than CompactFlash.
— CFexpress. Incredibly fast large-capacity drives designed for prolonged continuous recording in intensive mode. They are most suited for shooting video in 4K resolution and above at frame rates of 120 fps. Advanced series specimens provide writing and reading speeds exceeding 1 GB/s. Additionally, cards in this line are characterized by resistance to damage from drops and high bending strength. There are two types of CFexpress drives: Type A measuring 20x28x2.8 mm and Type B with dimensions of 38.5x29.8x3.8 mm.
— SxS. A memory card format developed jointly by Sony and SanDisk for professional-level video equipment. It uses the PCI Express interface, allowing such cards to be installed directly into an expansion card slot on a computer or laptop. It also features a high data transfer rate — up to 2.5 Gbps peak.
— PS Vita Card. A specialized memory card format designed, as the name implies, for portable gaming consoles PlayStation Vita. Created by Sony to replace UMD discs, it is not used by other manufacturers. It is proprietary, incompatible with universal standards like SD. The cards are available in capacities ranging from 4 to 64 GB.
— Nano Memory. A type of memory card introduced in 2018 by Huawei and mainly used in this brand's smartphones. Also colloquially known as nano SD, although this designation is technically incorrect. The size (area) of such media is 45% smaller than popular microSD cards, while Nano Memory cards are identical in size and contact placement to nanoSIM format SIM cards. This simplifies the use in smartphones with combined slots (suitable for both "sim" and memory card). As for characteristics, initially, Nano Memory was stated to have volumes up to 256 GB and reading speeds up to 90 MB/s; if this standard proves successful, we can expect these numbers to increase.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...general 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 data exchange 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 are quite compatible with equipment that does not have UHS - except that the speeds in such cases will be limited by the capabilities of the card reader, and not the card itself.
As for the 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 maximum data transfer speed (usually referring to read mode) depends on the UHS generation - 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 the slower standard.
Note that for UHS cards, more advanced characteristics may be indicated in other paragraphs - for example, the video recording class (see below) V90 for a UHS-II Class 3 card. There
...is no contradiction here: the speed of 90 MB/s provided by such a card in recording mode, it fully satisfies the “not lower than 30 MB/s” condition provided for UHS Class 3.Video recording class
The video recording class supported by the memory card.
This parameter is indicated for SD/microSD cards and their variations, as well as CompactFlash (see “Type”). In the first case, the format designation V* is used, in the second - VPG*, but the idea is the same in both cases: 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 recording, 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 SD/microSD family cards is
V6, which already allows you to work with HD and Full HD video. However, for Full HD it is advisable 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 for resolutions of 8K and higher.
In turn, in CompactFlash cards you can find models of the
VPG20,
VPG65 and
VPG130 classes
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 contradic
...tions here. UHS class requirements require write speeds of “not less than...”; Thus, for example, all cards with a video recording class of V30 and higher will comply with the UHS Class 3 standard (“not lower than 30 MB/s”). And the general speed class describes the capabilities of the card when working with equipment without UHS support (and such equipment is practically not used in video recording).Speed value
The coefficient describing the maximum speed of the card in read mode. In this case, 150 KB/s is taken as a unit; thus, for example, the speed value of 533x corresponds to 150*533=79,950 KB/s, i.e. about 80 MB/s.
In general, this parameter is quite specific; in practice, it is easier to focus on the directly declared reading speed (see below). However, sometimes it is not specified - in such cases, the speed value will be most 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.
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.
