How to choose a memory card | Articles | Photo, video, optics, Audio and video equipment


The time in which we live is different in that most of the knowledge of mankind is stored in digital form. Digital recording, as you know, is characterized by the fact that the amount of information can be accurately measured, since it has a discrete nature – in the form of so-called bytes. Naturally, the total amount of information is growing, and it must be stored and transmitted in some way.

To store information in compact portable devices, so-called memory cards are used. They are an electronic circuit enclosed in a rectangular protective case with remote contacts through which communication with the device takes place. The memory card is inserted into a special slot – a recess with return contacts.

Memory cards have two main parameters: capacity and speed.

It is most convenient to measure the volume of modern memory cards in gigabytes. As a rule, it has one of the following values: 8, 16, 32, 64 and 128 gigabytes. Other values ​​are less common.

As for speed, there are two important parameters here:

  1. Reading speed. Determines how quickly information will be read from the memory card. For example, when you insert a memory card into a computer and then copy files to it, the copy window will display this speed.

  2. Recording speed. This is the maximum file transfer rate to the card. This indicator is very important when used for photo and video shooting, as it shows what quality pictures or videos can be taken. The write speed is always less than the read speed.

Memory card with manufacturer-specified read and write speed

At first glance, the relationship between image quality for stills and videos and the speed of a memory card may not be obvious. Let’s explain.

Each photo occupies a certain amount of memory. And the camera can do a certain number of frames per second. Accordingly, a given number of frames of a known size should be written to the card per second. The write speed of a memory card is especially important for professional “quick-fire” cameras that shoot more than 10 frames per second. True, they have a so-called burst buffer – a certain amount of fast memory in the camera itself, which records photos initially. Already from the buffer they are written to the memory card.

With video shooting, everything is somewhat simpler: a video file has a so-called bit rate – the amount of information that is contained in one second of video. If the bitrate is greater than the recording speed of the memory card, the video will not be recorded, or it will be, but with frame loss and image defects. Therefore, buying a memory card that is too slow for this camera is, in its own way, throwing money away.

This is especially true for devices of new generations: for example, in modern action cameras, 4K video is already an industry standard.

Everything said about the speed of memory cards is also true for smartphones. It should be borne in mind that professional photo and video formats are not used here. However, common sense dictates that a slow memory card will be inconvenient to use, and 4K video is also found in modern smartphones.

So, we know the general concepts, it is worth moving on to the specifics.

To the delight of customers, the memory card standards that are now common are developed by companies independent of the manufacturers of the equipment itself, and by purchasing a memory card, you can use it in any similar devices. It should be noted that this was not always the case, and, for example, Sony and Olympus once released their own memory cards for their devices.

We list the current formats of memory cards.

SD cards

Perhaps 90% of the memory card market is occupied by this format and its varieties.

This happened, apparently, due to the small size of the cards themselves and the possibility of scaling the standard in accordance with the increasing requirements for speed and volume.

The fact is that the first SD memory cards supported a maximum volume of only 4 GB. However, this was clearly not enough, and a new standard appeared – SDHC – with a capacity of up to 32 gigabytes. Finally, the most modern standard – SDXC holds 64 gigabytes and above.

The controller of the SD memory card is not in the card itself, but in the device. Therefore, if the device was released before any of these standards appeared, then this standard will not work in this device.

As for the speed, the so-called classes were used here to measure it, denoting the minimum write speed in megabytes per second. The class is indicated by a number in a circle. Now all SDHC and SDXC cards are class 10.

A more modern classification is the so-called UHS standard, the class in which is indicated inside the letter U. The following types of cards can be distinguished here:

  • UHS-I Class 1 – 10 MB/s and above
  • UHS-I Class 3 – 30MB/s and above
  • UHS-II – 156 MB/s and above
  • UHS-III – 312 MB/s and above

SDXC UHS-I Class 3 memory card designation

However, you won’t have to guess with high-speed cards: manufacturers do not hide their advantages and indicate read and write speeds on the packaging.

On more budget models, we will see only one value, and this is the reading speed. The write speed can be roughly determined by dividing the read speed by two.

Smartphones and action cameras use a smaller version of this memory card format – MicroSD. Absolutely all the above features and characteristics apply to them.

The microSD card can be used in a device with an SD slot through an adapter.

MicroSDXC memory card with SD adapter

compact flash

This is one of the oldest memory card formats, which, however, is still used today. Its advantage is that the controller here is located in the card itself. Therefore, even old devices released, say, 10 years ago, can potentially work with new cards of large volumes.

Although the name of the standard contains the word “compact”, the cards themselves are not small by modern standards: 42 mm by 36 mm.

CompactFlash memory card (left) compared to SD card

Therefore, they are used in professional cameras and stationary devices, where this disadvantage is not critical.

The speeds of CompactFlash cards are also indicated directly on the package and label. Here we use the notation of the speed of the card in the form of a multiplier in the form of a number with the sign of the multiplication after it. 1x here means 150 KB/s. Some common multiplier values ​​are shown in the table:

133x 20MB/s
400x 60MB/s
1000x 150MB/s


These cards, although similar in appearance to CompactFlash, are completely different inside. The connector of these memory cards is nothing but SATA, which is used in computers to connect a hard drive. From this it becomes clear that speed was a priority when developing this type of memory card.

CFast memory card slot

And indeed, their speed lies in the range of 500-550MB / s, and they are used, for example, in professional video recorders.


An alternative to CFast, created at the initiative of Sony and Nikon and used in their cameras. Compared to Cfast, it has smaller dimensions, but also lower speed: 400MB / s and higher in write mode.

XQD memory card

Consider specific classes of devices and which memory cards are best to choose for them.


Not all smartphone models have the ability to install a memory card, but if it is, then everything is quite simple. Firstly, this is a MicroSD memory card, since it is it that has the most compact dimensions.

Most likely, a memory card in a smartphone will be used to store large files, since internal memory is enough for small ones. Therefore, the size of the memory card should be sufficient – from 32 GB.

As for speed, it most of all affects the usability, that is, the time required to copy files to it. If your phone has USB 2.0, the maximum theoretical port speed does not exceed 60 MB / s, so there is no point in buying a faster card.

With USB 3.0, you can also buy faster memory cards.

Camcorders, car recorders and action cameras

First, you should find out what format the memory card is used in your device. In the case of camcorders, this is most likely the SD format and its variations, action cameras and DVRs use MicroSD.

If you are a simple user, then it will be easiest to look at the video resolution.

If the camera uses “classic” FullHD, that is, 1920×1080, a card with UHS-I Class 1 speed class (class 10 according to the old classification) will suffice.

For 4K resolution – 3840 × 2160 – UHS-I Class 3 cards are recommended, the write speed of which is from 70 MB / s.

Professional camcorders use specific media such as P2, MicroP2, SxS Memory Card, Professional Disc media. Usually, such carriers are not widely available.

As for digital cinema cameras, here the camera is connected to an external recorder – a device that fully takes on the functions of encoding and recording a video stream.


Here, the choice of a memory card is highly dependent on which image format you have chosen.

No matter how expensive and sophisticated the camera is, if you are going to shoot in regular JPEG, almost any modern memory card (UHS-I Class 1 and higher) will do. The volume is also not so important, since the pictures take up little space – 5-10 MB.

If you shoot in RAW, the size of photos rises to 30 MB and more, SDHC and SDXC memory cards with speeds of 70-90 MB / s, as well as CompactFlash with high speeds, can be very useful for continuous shooting. If you are looking at UHS-II memory cards, you should be warned – not all cameras support it.

Professional reporting cameras use CFast (Canon) and XQD (Nikon) memory cards.

Conclusions and general recommendations

In any large hardware store, a huge assortment of memory cards is presented, the average user simply “dazzles”. In fact, this is because there are a sufficient number of manufacturers. Some of them have been around for more than 20 years, although their products are more expensive, they are 100% reliable. In addition, the speed of similar memory cards differs for different developers, if it is possible to gain several tens of megabytes per second in this way without increasing the price, the game is clearly worth the candle.

Many cameras have not one, but two memory card slots. In this case, it is better to use two memory cards in data duplication mode. This will keep the pictures safe and sound even if one of the memory cards breaks down.

Well, the last tip – never use a memory card as the only place to store important files. Always make backups.


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