Several years ago, there were only a few types of memory cards that were being used, particularly in the digital photo cameras – CompactFlash, SmartMedia and the cards manufactured by Sony. In the present days of global standardization, dozens of variations of memory cards have been conceived and manufactured by various companies and most of them are incompatible with each other. The CompactFlash cards were introduced ever since 1994 by the SanDisk Company. These cards are still available on the market and are used for the digital SLRs (Single-Lens Reflex). There are two types of CompactFlash cards – type I and type II – and the only difference between the two is given by the thickness of the finite product. Most digital cameras allow the usage of CompactFlash type memory cards and they are available generally in their 8 GB versions. The memory cards are also being used in mini hard drives or the so-called MicroDrives, initially developed by IBM Corporation. The MicroDrives were very popular several years ago because they had a high storage capacity and they were offering an increased transfer speed. Recently, the Hitachi Company announced the launch of a 20 GB microdrive that uses the perpendicular data recording technology.
The SmartMedia memory cards were introduced in 1995, but they were forgotten quite fast due to their low storage capacity which was usually 128 MB – enough for a maximum of 30 pictures. The SmartMedia memory cards were thin, which means they were prone to rapid deterioration and their usage was dropped altogether as in the last 6 years virtually nobody has ever used them.
The moment the producers realized the inefficiency of the SmartMedia memory cards, they switched to the SecureDigital formats with the notable exception of Fujifilm and Olympus, decided to introduce a whole new memory card, xD-Picture, launched in 2002. This type of card had the advantage of being smaller than a SD and theoretically had a storage capacity of up to 8 GB, unlike the SecureDigital type who did not have at that point more than 512 MB in storage capacity. The Fujifilm and Olympus corporations were hoping that their new card was going to be used by most of the companies that were manufacturing digital cameras – but their hope did not become true after all. Eventually, Fuji themselves launched cameras with slots both for xD and SD cards, which was the sign that they were starting to lose their confidence in their own product.
The Secure Digital type memory cards were launched in 1999 by Panasonic, Toshiba and SanDisk, and were based on the already existent technology – the MultiMedia format (MMC), which had been designed two years before by the SanDisk and Siemens corporations. The name of the card comes from its capacity to encrypt audio formats. It is being used nowadays for most of the digital cameras available on the market and even for other products such as the DRLRs (Digital Single-Lens Reflex), video cameras, mobile phones, palmtops and mp3 players.
In 2006, the improved version of the SD memory card was launched– called SDHC (High Capacity), which was capable of storing an extra amount of 2 GB and had a capacity of reading and writing which was much higher in comparison with the simple SDs. Most of the digital cameras compatible with SD memory cards are also compatible with SDHC memory cards, but it is nonetheless recommended to check the compatibility prior to acquiring a new memory card.
The Sony Corporation also has its own brands of memory cards as the original memory card, called Sony Memory Stick, was launched in 1998. That card had a storage capacity of only 128 MB and this is why it was replaced several years later, in 2003, by the new Memory Stick Pro, which was conceived in collaboration with the SanDisk Corporation. Sony is constantly improving its products and, shortly after, they launched the memory card called Stick Pro Duo which had smaller dimensions and was similar, to a certain degree, with the SD type card, and after that they launched an even smaller memory card called Stick Macro and in the same time they launched the super fast Stick Pro HG, which was available on the market until quite recently. These cards are being used for the digital cameras manufactured by Sony and are, generally, slightly more expensive than the SD memory cards, albeit they have similar storage capacities.
The number of pictures that can be stored on a memory card used in a digital camera is hard to be approximated. The majority of the digital cameras are using for storage the JPEG format that compresses the images in order to save the storage space from the memory card – but the degree of compression varies a lot depending on the nature, clarity, settings and the quality of the image. For a compact camera of 7 MP, with the quality settings placed on maximum, the dimension of the files varies between 2 MB and up to 4 MB per picture with a constant average around 3.5 MB. For the same compact camera of 7 MP, the pictures made using low quality standards can have up to three times smaller dimensions in comparison with the images made on high standards. Due to these factors, a memory card with a storing capacity of 1 GB can store between 200 and 800 images.