memory card wala speed eka,class 2,4,6,10 wage thiyanawa neda. Thawa UHS 1,....wage ewa thiyanawa..menna meketh podi wistharayak thiyanawa.
http://www.flashtech.lk/p/speed-class-in-nutshell-not-all-sd.html
Speed Of Memory Card
Speed Class
In a nutshell, not all SD cards offer the same speeds. This matters for some tasks more than it matters for others. For example, if you’re a professional photographer taking photos in rapid succession on a DSLR camera saving them in high-resolution RAW format, you’ll want a fast SD card so your camera can save them as quickly as possible. A fast SD card is also important if you want to record high-resolution video and save it directly to the SD card.
If you’re just taking a few photos on a typical consumer camera or you’re just using an SD card to store some media files on your smartphone, the speed isn’t as important.
Manufacturers use “speed classes” to measure an SD card’s speed. The SD Association that defines the SD card standard doesn’t actually define the exact speeds associated with these classes, but they do provide guidelines.
There are four different speed classes — 10, 8, 4, and 2. 10 is the fastest, while 2 is the slowest.
Class 2 is suitable for standard definition video recording, while classes 4 and 6 are suitable for high-definition video recording. Class 10 is suitable for “full HD video recording” and “HD still consecutive recording.”
There are also two Ultra High Speed (UHS) speed classes, but they’re more expensive and are designed for professional use. UHS cards are designed for devices that support UHS.
Here are the associated logos, in order from slowest to fastest:
You’ll probably be okay with a class 4 or 6 card for typical use in a digital camera, smartphone, or tablet. Class 10 cards are ideal if you’re shooting high-resolution videos or RAW photos. Class 2 cards are a bit on the slow side these days, so you may want to avoid them for all but the cheapest digital cameras. Even a cheap smartphone can record HD video, after all.
An SD card’s speed class is identified on the SD card itself. You’ll also see the speed class on the online store listing or on the card’s packaging when purchasing it.
If you see no speed class symbol, you have a class 0 SD card. These cards were designed and produced before the speed class rating system was introduced. They may be slower than even a class 2 card.
It’s important to remember that Speed Class and UHS Speed Class are two different speed indication symbols for different devices. However, a UHS-I memory card may also indicate a Speed Class.
The host device Speed Class requirements are minimum requirements for optimum performance. If your host device requires a Speed Class 4 SD memory card, you can use Speed Class 4, 6 or 10 SD memory cards. If your host device requires a Speed Class 6 SD memory card, you can use Speed Class 6 or 10 SD memory cards.