SD vs SDHC memory cards
Secure Digital (SD) Cards have been in the market for around 10 years, Secure Digital High Capacity (SDHC) Cards are the advanced version made for the need of higher capacities as well as faster data transfer rate in digital cameras and other such devices. SDHC cards are designed for devices that are compatible with the SD 2.00 specification. Products designed exclusively to support previous SD specifications 1.0 and 1.1 will not be able to fully utilize SDHC cards. To check whether your device is SDHC compatible, look in your device manual or on the packaging/box for the SDHC symbol.
SD – Secure Digital card capacities range from 8 MB to 4 GB and SDHC – Secure Digital High Capacity memory cards are flash memory cards with a minimum capacity of 4GB (gigabytes)!
SD and SDHC cards are a removable storage solution for compatible digital devices including digital cameras, camcorders, MP3 players, PDAs and more.
The increasing demand for high-capacity flash memory springs partially from the use of high-definition video and high-resolution digital photography, SDHC cards meet the challenge of these demanding products not only by providing greater storage but also by faster data transfer speed
Shape and Size
SD and SDHC cards look identical in size and shape, only SDHC-compatible cameras and devices can accept the new SDHC cards. Manufacturer differentiates its new cards with the SDHC logo on the card and retail package.
Data Transfer Speed
Users can get the maximum performance of their digital products by using digital memory cards that support the device’s highest data transfer speed.
The Secure Digital (SD) card falls in three Classes according to Data Transfer Speed (DTS) as follows:
Class 2: minimum sustained DTS of 2MB/sec (13x Speed)
Class 4: minimum sustained DTS of 4MB/sec (26x Speed)
Class 6: minimum sustained DTS of 6MB/sec (40x Speed)
The issue with these memory cards is that if the card has a write speed of 6MB/Sec or 40x Speed, then thats the maximum speed not the average speed.Lets say the device (eg. camera) will start writing the image or data to the card at 0MB/sec and then work up to the top operating speed of 6MB/sec and then slow down again to 0MB/sec as it finishes writing the data, thus meaning the average write speed may be around 3MB/Sec.
Secure Digital High Capacity (SDHC) cards have a guaranteed minimum write speed of say 6MB/Sec (40x Speed) will start at this speed and may in fact have a higher top speed – like the SanDisk Extreme III Secure Digital Card – SDHC 4gb Memory Card, this is a Class 6 card -therefore having a minimum sustained write speed of 6MB/Sec – 40x Speed, but has a top speed of 20MB/Sec – 133x Speed.
This means that the SDHC card starts writing data at a specified speed and sustain that speed, whereas regular SD Cards start writing data at 0MB/Sec and build up to a top speed; SDHC memory cards start writing the data at a higher minimum speed.
SD and SDHC Extra Features
Secure Digital(SD) cards were forced to create a new specification for SDHC cards when the previous specifications reached out at a highest capacity of 2GB. This occurred previously when SD cards hit the 512MB wall. The new 2.00 specification should last a bit longer, as it allows SDHC cards to reach a maximum capacity of 32GB. Secure Digital is so-named “Secure” because of its ability to protect copyright content through Digital Rights Management (DRM). Thats why it is the favored flash memory format in the industry.
But before purchasing a SD or SDHC memory card, make sure your device is compatible. If a device manual does not list SDHC cards, or state it is “SD specification 2.0 compatible,” the device cannot work with SDHC cards. Remember, if your device accepts SDHC cards, it is backwards compatible with standard Secure Digital (SD) cards too.