What is the difference between SD, SDHC, SDXC?

SD, SDHC, SDXC. Class 2, Class 6, Class 10. Variety, we have loads of Micro SD Card For Kindle Fire 8  in the world. But which one should be used in our camera? Which one in the video? What will be the impact of a faster card? This is what we will see today.


SD, micro SD and mini SD cards are a world standard, maintained by the SD Card Association. This format was initially developed by SanDisk, Matsushita, and Toshiba.

This format was an evolution of MMC cards (originally from SanDisk and Siemens AG) which, at the time of introduction to the market, were significantly smaller than other cards of the time, such as CompactFlash. MMC cards are, at first glance, practically identical to current Secure Digital cards, except for a variation in thickness (1.4mm for MMC versus 2.1mm for SD).

Being a standard, the SD quickly gained popularity, surpassing the Memory Stick, controlled by Sony. And today it is, in fact, one of the most used formats in a wide variety of products, ranging from digital cameras, to cell phones (in its microSD version), to camcorders, and much more.


In addition to the traditional SecureDigital (SD), we have two other varieties of size, miniSD cards, and microSD cards, the latter being more popular, due to the compactness of the size.

Popular models are the regular size (SD), used in cameras, camcorders, and microSDs, used in smartphones, and even some compact cameras. While there are miniSDs (and adapters for microSDs to work on miniSDs or as SDs), devices that use the intermediate size are almost non-existent today, due to not offering any advantage.

One of the questions in this regard is usually if there is a speed impact if we use a microSD card, with an SD adapter (to function as a “regular size). The answer? There is no difference, because all this depends on the classes, which we will see next.

Classes and Storage

The speed of the cards is divided into “Classes”, which go from lowest to highest. Thus, for example, we have Class 2, Class 4, Class 6 and Class 10. The number that accompanies each class means the card’s writing speed. Thus, a Class 2 card ensures us, at least, 2 MB / s of writing, while a Class 4, will record at 4 MB / s, and a Class 10, the fastest, will record at least 10MB / s It is important be guided by the classes, because the figure that we find on the cards, in MB / s, usually tells us the reading speed , which is always much higher than the writing speed .

It is important to keep this in mind because different kinds of memories have different uses.

For a video camera, even recording in Full HD, a Class 4 is enough. This is because video cameras / camcorders use the AVCHD or MP4 format. Both formats compress video, so a card with high write speeds will hardly be needed. Videos in AVCHD or MP4, for example, especially in “High Profile” or higher quality, need 24Mb / s (which is equivalent to 3 MB / s). This means that a Class 4 card (which has a minimum write speed of 4 MB / s (Megabytes per second), equivalent to 32 Mb / s (Megabits per second), is more than enough.

For a still camera, a high class card, such as Class 10 or 6 is important. It sounds strange, but for a camera, we will need a card of a higher class. This is because, unlike video, where a constant speed is maintained during filming, a still camera needs a fast write speed to successively capture images. Nowadays, with the number of megapixels cameras have (16.18.20 mpx), it is not surprising, for example, that an image, even compressed in JPEG, ends up weighing 3-5 megabytes. And if you shoot RAW, we are talking about files that will weigh 20-35 megabytes per image.

Now, the cameras have a “buffer” or temporary memory, where to store the images to allow us to take pictures continuously and quickly, regardless of the class of the card. But there comes a time when this buffer fills up, and this is where we will notice the true impact that the class of our card has. They can do the test with the camera they have at home and the SD card, for example. Put your camera in “continuous” mode and shoot a number of photos in succession. Eventually, they will find that they can no longer photograph (perhaps with a “Memory Full” message), or they may be able to photograph, but with a long delay between photos. This is where you will see the great impact of a class 10, for example, that it will allow us to maintain a constant writing speed and, therefore,

For a smartphone / tablet, it depends on how we use it. By this I mean that, if you are only going to load the card with music and videos (that is, as extra storage for our multimedia files), having a very fast card does not help much. If, however, you are using it to store application files (such as sending the photos directly to the SD, instead of the internal phone memory, or storing the games on the card), a higher speed card, such as a Class 6, it’s worth it. This will prevent loading times from being too long, and will improve the overall experience.


Summing up, then:

  • Camcorders – Class 4
  • Cameras – Class 6/10
  • Smartphones / Tabelts – Depends on use (class 2/4 for multimedia, class 6/10 if we use it to store photos / games)


In addition to variations in size, we have variations in card types, which we will see below. We could consider the Types of SD cards as generations, and with each generation, the arrival of greater capacity.


  • SDSC (SD) – Original SD card, ranging from 1MB to a maximum of 2GB of storage.
  • SDHC – HC comes from High Capacity, and brought with it 4 GBs cards , up to 32 GBs of storage.
  • SDXC – XC comes from Extreme Capacity, it is the current format, and it takes us from 32 GBs to 2 Terabytes (2,000 Gigabytes) of storage. So we will have SDXC for a while.

Not all devices are compatible with all cards. If you have a device manufactured within the last 3 years, it probably supports SDXC cards from 64GB and above. But this already depends on the device (several smartphones, for example, only have support for SDHC cards). But if you have a device with SDXC support, you can also use traditional SDHC or SD cards. That is, new devices are compatible with the cards of the past.

Eye-Fi ?


Now that we know the types of memory, capacities, and even some history of SD cards, it seemed relevant to me to also mention the Eye-Fi , which you could see in the initial image.

This is a modification of traditional SD cards, which incorporate a WiFi antenna on the same card. So is; This SD card is capable of wirelessly transmitting images to the PC / smartphone / tablet, either by connecting to an existing Wi-Fi hotspot, or by generating one so that we can directly connect our phone to the card and transmit the photos.

The technology is extremely interesting, as it basically turns any camera into one capable of transmitting photos via WiFi (as long as the camera is compatible). I have been using it these days with the different cameras that I have to review, and it has been a blast just getting to the PC, and seeing that all the photos are waiting for me, ready to be observed. We will have a more complete review of the card soon.

you cam also check this article

“Pirate” memories, and how to detect a fake SD Card.

One of the side effects of the enormous popularity of SD cards is that the number of fake cards has not only grown to an alarming level, but the copies have become so similar – externally, at least – to the originals, that Distinguishing between an original and a copy is sometimes extremely difficult.

The best advice? Buy from a trusted place. Don’t look for great deals on eBay or Mercadolibre, as it will be difficult to determine their authenticity. Also, it is important to check the packaging; official SanDisk and Kingston cards are sealed on the packaging, while fake cards are usually glued.

If you have a smartphone on hand, check the barcode on the packaging, which will help to verify if it is a genuine card or not.

The problem with fake cards is that, in addition to lower capacity (in some cases), we will also end up with an inferior card, since it probably has not passed the necessary tests to be considered one class or another. It is a risk that is not worth taking, especially if we are looking for the right card for our camera. And nobody would like to lose all the photos taken, because of a false card that just happens to fail in the middle of our vacation, right?


What brand to buy?

I’ve been quite lucky with both SanDisk and Kingston, the most popular brands, and I have no problem recommending either one.

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