Micro sdhc what does class mean
The Official SD Association memory classification also includes a category for optional content security features, which enable SD memory cards to be used as storage for content-protected audio, video and books. As an example for demostration purposes, Class 2 is sufficient for SD video recording, whilst Class 4 and Class 6 support HD recording. The Class rating is displayed on the card, by a number nested inside a circle. After the Class 10 classification, it becomes a little more complicated. An additional standard called UHS was introduced, which allows cards to reach higher speeds.
UHS speed classes are shown on the card with a number inside a U. Some cheaper action cameras will buffer the recording, but this is not practical in the slower card speed classes, and may cause juddering or stuttering of the recorded footage, as well as other issues. Similarly with the latest Digital SLR Cameras especially in modes such as sport, multi-frame or burst-mode where multiple images are taken, having a faster card will allow you to review the images much sooner less waiting for the images to write to the card.
As a disclaimer, most devices such as cameras, mobile phones and card readers will generally work with older SD Cards , but newer SD Cards with higher Class and Speed classifications may not work in these older devices — check your owners manual or Search online for compatibility for cards that work with your device before purchasing.
Also Full-size SD cards and Micro SD cards may not work in devices that are specifically designed for one or the other, even though smaller cards can fit into larger card slots via adapters see the section below.
SD bus speed of The SD Association has defined various Speed Class standards to answer a demand for advanced video quality recording. Speed Class symbols indicated to host and card products help users decide the best combination for reliable recording no frame drop.
There are three kinds of speed indications:. This is mainly useful for camcorders, video recorders and other devices with video recording capabilities. Regarding bus mode, it is necessary to use a bus mode fast enough that does not affect memory write speed. Video Speed Class is defined to answer a demand for high resolution and high quality 4K8K video recording and it also has an important feature to support next generation flash memory such as 3D NAND.
SD Speed Class. All SD cards use the little brass contacts at the end of the package to receive and send information, in the form of instructions and data. The interface between the card and the reading device has evolved with each specification revision -- in some cases, the updated system just runs faster i.
The differences between all the interfaces and performance are set out in so-called speed classes , and each one is generally organized by the peak bus throughput.
This is a measure of the maximum amount of bytes per second that can be transferred between the SD card and host device. A microSD card sporting an extra row of contacts, for more performance.
Image: Wikipedia. However, not all NAND flash chips are the same, so the speed classes also indicate the minimum sequential write rate -- the slowest speed at which data can be put onto the memory chip in a structured, rather than a random, way. With so many speed classes to get your head around, it can be tricky to figure out what rating you really need.
In the table below, we can see how they roughly compare. The SD Association came up with the speed classification systems to help differentiate what cards are best suited to what purposes. With SD Specification 5. At that speed, the playback and recording of 8K video at 60 to fps becomes feasible. UHS-I cards have just one set of contacts for sending and receive information, so when running at the higher speed, the bus will run in what is called Half Duplex mode: the SD card will only be able to receive or send data, at any one time.
The later versions of UHS sport extra contacts, which permits Full Duplex send and receive together , both to occur at the same time; however, in UHS-II this results in the bus being forced to run at the slower speed. But this is because the performance is only unlocked if the device using the card fully supports it.
The table below shows how various cards will function in different UHS card readers, and indicates how SD Express would compare.