All you need to know about SD-memory cards, not to screw it up when buying
How To Choose Technologies / / December 19, 2019
1. Compatibility
For most people, microSD - it is only the form factor, but in fact it is not. You can easily insert any microSD-cards into a standard slot, but not every one will work, because the cards are distinguished by a variety of symptoms.
Format
There are three different SD format, available in two form factors (SD and microSD):
- SD (microSD) - drives up to 2 GB, work with any equipment;
- SDHC (microSDHC) - Storage of 2 to 32 GB, operate on devices that support SDHC and SDXC;
- SDXC (microSDXC) - drives from 32 GB up to 2 TB (currently a maximum of 512 GB), only work on devices with SDXC support.
As you can see, backward compatibility they do not. Memory cards of the new format will not work on older hardware.
volume
Declared by the manufacturer support microSDXC does not mean support for cards of this format with any volume, depending on the particular device. For example, HTC One M9 works with microSDXC, but officially only supports cards up to 128 GB or less.
With the volume of storage is connected is another important point. All microSDXC cards use default exFAT file system. Windows supports it for more than 10 years, she appeared OS X starting with version 10.6.5 (Snow Leopard), Linux-distributions in support exFAT implemented, but "out of the box" works not everywhere.
High-speed UHS interface
Cards SDHC and SDXC formats can support the interface Ultra High Speed, which in the presence of hardware support on the device provides a high speed (UHS-I to 104 MB / s and UHS-II to 312 MB / s). UHS backward compatible with older interfaces and may not work with its supporting devices, but at a standard speed (up to 25 MB / s).
2. Speed
Classification write speed and read microSD-cards in the same complex as their formats and compatibility. Specifications allow us to describe the speed charts in four ways, and because manufacturers use them all, there is a lot of confusion.
speed class
To speed class (Speed Class) the minimum recording speed is tied to the memory card in megabytes per second. There are four:
- Class 2 - from 2 MB / s;
- Class 4 - from 4 MB / s;
- Class 6 - 6 Mb / s;
- Class 10 - 10 MB / s.
The cards running on high-speed UHS bus while only two speed classes:
- Class 1 (U1) - from 10 MB / s;
- Class 3 (U3) - 30 MB / s.
Since the speed class designation record the minimum value, theoretically second class map may well be faster fourth card. Although, if it is so, the manufacturer will likely prefer more clearly indicate this fact.
full speed
Class speed is enough to compare when choosing a card, but some manufacturers use besides him in the description of the maximum speed in MB / s, and not even write speed more often (which is always below), and the speed reading.
Usually this synthetic test results under ideal conditions, which are unreachable during normal use. In practice, the speed depends on many factors, so do not rely on this feature.
speed multiplier
Another version of the classification - this is the multiplier rate, similar to that used to specify read and write speeds of optical disks. A total of more than a decade, from 6x to 633h.
Modifier 1x is 150 kb / s, i.e. in the simplest 6x cards speed is 900 KB / s. At the fastest card factor can be 633h, which is 95 MB / s.
3. Tasks
To choose the right card, taking into account specific problems. The biggest and fastest is not always the best. In certain scenarios, using the volume and velocity may be excessive.
When you purchase the card for the amount of smartphone plays a greater role than speed. Plus a large storage are obvious, but the benefits of high speed transmission on a smartphone is almost not felt, because there are rarely written to and read from files of large volume (unless you do not have a smartphone with support 4K-Video).
Camera, relieving HD- and 4K-video - is another matter: it is equally important and the speed and volume. For 4K-video camera manufacturers recommend using a card UHS U3, for HD - ordinary Class 10 or at least a Class 6.
For photos, many professionals prefer to use multiple maps smaller volume in order to minimize the risk of losing all the images in the case of force majeure. With up to speed, it all depends on the picture format. If you shoot in RAW, it makes sense to invest in a microSDHC or microSDXC Class UHS U1 and U3 - in this case, they reveal themselves to the fullest.
4. forgery
As corny as it may sound, but buy a fake under the guise of the original maps is now easier than ever. Several years ago, SanDisk announced that a third of SanDisk memory cards on the market is counterfeit. It is unlikely that the situation has changed dramatically since that time.
To avoid disappointment when you buy enough to use common sense. Refrain from buying from sellers, not credible, and beware of sentences "original" card, the price of which is significantly lower than the official.
Attackers have learned to forge packaging so well that sometimes it is very difficult to distinguish from the original. With full confidence to judge the authenticity of a card is possible only after checking with the help of special tools:
- H2testw- for Windows;
- F3 - for Mac and Linux.
5. Quality
If you have already experienced the loss of important data due to memory card failure, for whatever reason, then, when it comes to choice, you are likely to prefer a more expensive card-known brand than available "Nouneym".
In addition to greater reliability and safety of your data, with branded card you get high performance and guarantee (in some cases even lifelong).
Now that you know about the SD-card everything you need. As you can see, there are many questions that you will have to answer before buying a card. Perhaps the best idea is to have different cards for different purposes. So you can use all the advantages of the equipment and do not expose your budget unnecessary costs.