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SDHC Card Class Difference

Omkar Phatak
If you are looking for information about SDHC card class differences, you have landed on the right page. Read to get an idea about how SDHC cards are classified into different classes, according to the data transfer speeds which they offer.
Anyone who has a digital camera or camcorder has used a SDHC memory card. Let's have a look about the class differences in SDHC cards and why it's an important factor to be considered while buying them.

About SDHC Memory Cards

SDHC (Secure Digital High Capacity) cards are non-volatile data storage devices. They were designed for use in portable devices like PDAs, digital camcorders, digital cameras, netbook computers and other devices like video game consoles. They are the second generation of SD cards developed after the earlier line of cards reached a storage capacity limit.
SDHC cards have a maximum storage capacity of 32 GB. The storage capacities offered are 4 GB, 8 GB, 16 GB and 32 GB. These cards are not compatible with earlier SD host devices. However, the first generation SD cards can be used on SDHC host devices.
Storage capacity of SDHC cards is not the only feature to look out for, while buying one. Besides differences in manufacturing brand, you need to take the class difference into consideration. When you understand these class differences, you will be able to distinguish HD camcorder SDHC cards (also known as video cards), from ordinary digital camera cards.

SDHC Memory Card Classes

As the demand for SD cards grew, they started being used in a wide variety of devices. The data transfer speed demanded by different devices varied. To cater to the specific data transfer speed requirements of these devices, SDHC cards were produced with different speed specifications.
All these cards are not created equal. They are differentiated into classes, according to a 'Speed Class Rating'. This ensured that a device in which a SDHC memory card was fitted, was able to fully utilize its capacity.
The declaration of the SDHC specification 2.0 created an official classification of SDHC cards, according to data transfer speed (DTS). The differences are purely based on the speed of data transfer. The SDHC memory card classes along with their maximum possible data transfer speed are as follows:

SDHC Classes


SDHC Class 2:
Speed: 2 MB/sec (16 Mbit/sec)
Ideal For: Low Resolution Digital Cameras

SDHC Class 4:
Speed: 4 MB/sec (32 Mbit/sec)
Ideal For: Medium Resolution Digital Cameras and Standard Definition Camcorders

SDHC Class 6:
Speed: 6 MB/sec (48 Mbit/sec)
Ideal For: High Resolution Digital Cameras and High-Definition Digital Camcorders

SDHC Class 10:
Speed: 10 MB/sec (80 Mbit/sec)
Ideal For: High Resolution Digital Cameras and High-Definition Digital Camcorders

SDHC Class 16:
Speed: >16 MB/sec (128 Mbit/sec)
Ideal For: High Resolution Digital Cameras (DSLR) and High-Definition Digital Camcorders
The last two classes (SDHC Class 10, Class 16) were introduced recently by Pretec, Panasonic and Toshiba to cater the high data transmission speeds required by HD camcorders and DSLR cameras. It is essential that you read the specifications of a SDHC memory card, before you buy it.
The cost of these memory cards vary according to the data transfer speed. The cards with the fastest data transfer speed are the class 10 SDHC cards while the ones with the lowest data transfer speed is the class 2 card. If you make a SDHC class 6 comparison with the class 10 cards, the difference in their speed won't affect camcorder performance a lot.
It is important that the device data transfer speed requirements match with the right card class for smooth functioning. If you do not take the class difference into consideration while buying it, the functioning of the device may not be up to the mark.
If you have a high-definition camcorder which requires you to have a class 6 card and you fit it with a class 2 card, the speed of recording stream of the device may not match with the data transmission speed, causing synchronization problems.
On the other hand, if you have a basic digital camcorder for which you buy a class 6 SDHC card, it would be a waste of money as that device may not be able to take advantage of the high data transfer speed. That's why, make sure that you know the class differences and buy a card accordingly.
SDXC cards, released recently, are an improvement over SDHC cards. They will eventually offer up to 2 TB of storage capacity. At present, SDXC memory cards, with a storage capacity of 64 GB and 128 GB have already been made available in the market. These cards will offer data transfer speeds, which will be superior to what their predecessors offered.
A glance through the specifications of a memory card or device will tell you all about its data transferring ability or requirements.