General type of memory card.
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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, whil...e by default 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.
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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.
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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 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.
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.
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.
The ability to switch the card to read-only mode, which allows you to protect important data from accidental overwriting or erasure. Usually implemented in the form of a mechanical slider switch, the position of which determines the card's operating mode. However, it is worth considering that this slider is only an indicator that signals the card reader about the selected mode, and its position does not affect the card itself; in some card readers,
the write protection function may simply be absent - such devices will not "see" the position of the slider.
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.
