Tag : flashdrives

Understanding the prints on SD ( or microSD) card


Which SD card should I choose ?

Which SD card should I choose ?


Everytime we look at a SD (microsd) card, we see a whole of information printed on it. Do you know what all these printed information mean? Well, the most obvious one is the storage space ( 2GB, 4GB, 8Gb etc). What about the rest? Are they important to know?

Let’s take a closer look at the SD (microsd) cards this time round.


Does SD (microsd) card speed make a difference?

Everyone knows that SD and micro SD card speed makes a difference in read and write speed. But is it really that important? And what exactly do they actually do? Is the class number higher the better?

Well, it all depends on what you wish to use the SD ( or microSD) card for.

Many Uses for SD and Micro SD card

Nowadays, many cameras and mobile phone uses these removable media to store pictures and information. In fact, many IP surveillance cameras now use these removable storage for recording the video footage. Also in-car video cameras also widely use these media for storage as well.

These SD ( or microsd) cards are small, easily removable and pass around as well, so they are very popular and widely used.


The classification number

As many of us would have noticed, there is quite a number of information printed on these cards other than amount of storage. These numbers and information also determine the different pricing for the cards.

Broadly speaking, there are four different types of classes: 2, 4, 6, 10. Class 2 being the slowest and Class 10 being the fastest. Nowadays, with the pricing of removable media going down, the most common class usually starts from 4 onwards. There is also another category now called UHS (Ultra High Speed) Class.

Referring to the definition stated in SD association website:

“Speed Class and UHS Speed Class* symbols indicate minimum writing performance to ensure smooth writing of streaming content such as video shooting.”

“Speed Class designates minimum writing performance to record video. The Speed Classes defined by the SD Association are Class 2, 4, 6 and 10.”

“UHS Speed Class is designed for UHS** devices only and designates minimum writing performance to record video on UHS products. The UHS Speed Classes defined by the SD Association are UHS Speed Class 1 (U1) and UHS Speed Class 3 (U3).

* (Speed Class and the UHS Speed Class are not compatible.)

**UHS (Ultra High Speed), the fastest performance category available today, defines bus-interface speeds up to 312 Megabytes per second for greater device performance. It is available on SDXC and SDHC memory cards and devices.”

SD Card comparison Table

SD Card comparison Table


For more detailed info, below is link:


So if we use the table from SD association as a guide, for standard camera and video recording, we can use up to class 6. For those devices that requires HD video and continuous shooting (hence higher write speed) , we should buy class 10 and above cards.

UHS type of cards will be for people who needs to shoot higher resolution video and likewise their pricing is also more expensive.

Usually, the product which you intend to use with the SD (or microsd) card will also have guidelines on the ideal speed and class, so do read the manual carefully before you purchase the removable media.


Read and Write Speed

There are two types of speed involved, one being write speed ( rate at which data is being transferred to the media) and another being the read speed ( The rate at which the data is being retrieved off the media). The speed provide by SD card association is meant to be used as a general guideline and you will have noticed different SD ( or microSD) brand manufacturers also produces difference details printed on their products.



What is the difference between SD and SDHC card?

For those who started using removable media some years back, you will most probably noticed that we used to have only SD card as a standard. Recent years, we started seeing only SDHC cards and not SD card anymore.

The main difference is that SD card maximum supported storage is only up to 2GB. SDHC card starts from 4GB onwards.

Older devices such as cameras will sometimes only accept SD card and if a SDHC card is inserted, the device will not be able to recognise the presence of the card, hence it will not work. On the other hand , SDHC devices can recognise SD cards, and is downward compatible.

Basically, SDHC cards and SD cards are of the same physical size but SDHC cards meets with the new SD specification version 2.0.


Higher resolution video equals to more storage space required

So if you are going to take high resolution video such as 4K videos, then you will have to buy UHS speed type of card for better performance. Of course the higher the resolution of the video or pictures, the more space it is going to take in terms of storage, so do take that into consideration as well when purchasing these flash media.

That’s it. Hope to bring more useful information to you in our next article.