SD vs SDHC Flash Cards

SD vs SDHC flash cards, what are the differences? There are several types of flash storage media available in the marketplace. Each different type of media was designed for a specific purpose, although in many cases, the uses can be interchangeable.

Types of Flash Storage

Before discussing the differences between SD vs SDHC flash cards, this section lists some of the other popular types of flash storage media. 

First there is the USB flash drive. Its introduction was in 2001 and it is very popular for moving files from one computer to another, but is also gaining momentum as a storage device for backing up computer files. The USB flash drive page discusses this format in more detail.

Next is the Solid State Flash Drive or SSD. This is a storage device used internally or externally as the main storage device in desktop and laptop computers. The Solid State Drive was introduced in 1995, but only recently has begun to gain popularity in the consumer marketplace and started to replace the more common hard disk drive, which has been popular for many years.

Another well used flash storage medium is the Compact Flash Card or CF Card. The introduction of this card was in 1994 and its use is almost exclusively with SLR digital cameras. The popularity of this format has decreased due to the increase in popularity of the Secure Digital or SD flash card family.

SD vs SDHC Cards

When it comes to this group of flash storage card media, there are a variety of different types. First there is SD vs SDHC. These two are essentially the standard type of cards. SD stands for Secure Digital and its introduction to the marketplace was in 1999. The capacity of SD cards is up to 2 GB.

A Kingston 1 GB capacity SD or Secure Digital card. This flash card is used in digital SLR cameras to provide more storage capacity for the camera.

Now if comparing SD vs SDHC, the latter cards are higher capacity versions of essentially the same format of card. The SDHC or Secure Digital High Capacity card was introduced in 2006. The capacity of the SDHC card is greater than 2 GB and up to a maximum of 32 GB. 

A Lexar 32 GB SDHC card or Secure Digital High Capacity card used to provide additional storage in SLR digital cameras.

One major difference between SD vs SDHC flash cards is that the write speed designation of the SDHC card is printed right on the label. For the Secure Digital High Capacity Cards, a number inside of a capital “C” represents the speed. The speeds are:

  • Class 2 (C2) – a minimum of 2 MB/sec write speed
  • Class 4 (C4) – a minimum of 4 MB/sec write speed
  • Class 6 (C6) – a minimum of 6 MB/sec write speed
  • Class 10 (C10) – a minimum of 10 MB/sec write speed

These formats are used extensively with digital cameras for the storage of digital photographs.

Other Secure Digital Card Formats

In addition to SD vs SDHC flash cards, there are also other variations. For example, there is also the SDXC card or Secure Digital Extra Capacity card. This flash card format came to market in 2009 and has a capacity range between 32 GB and 2 TB. The write speeds for these cards are presented as a number inside of a capital “U” and can be U1 (a minimum of 10 MB/sec write speed) or U3 (a minimum of 30 MB/sec write speed).

The even higher capacity SD card, introduced in 2018, is the SDUC or Secure Digital Ultra Capacity card. The storage capacity range is from 2 TB to 128 TB. The write speeds on the cards are identifiable as a capital letter “V” with the following numbers beside it – 6, 10, 30, 60, and 90 MB/sec. These are minimum write speeds.

Micro SD Card Formats

In addition to the standard SD and SDHC cards, there are also microSD cards. These are substantially smaller flash storage cards used in devices such as cell phones. 

A 2 GB microSD card. This card is substantially smaller than a standard SD card and used in devices such as cell phones to add more storage capacity.

Focusing solely on the SD vs SDHC micro flash cards, there are a few differences. The microSD card was introduced in 2005 and the microSDHC card in 2007. In terms of storage capacities, they are like the standard size SD and SDHC cards. MicroSDXC and microSDUC are available as well. The properties of all these smaller formats are similar to their larger versions

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