Storage of Photos and Videos on Digital Cameras

Some higher-end professional cameras use PCMCIA hard disk drives as their storage medium. Although they consume no power once images are recorded, and have much higher capacity than flash memory (a 170MB drive is capable of storing up to 3,200 images standard 640 by 480 images), the hard disk option has some disadvantages. An average PC Card hard disk consumes around 2.5W of power when spinning idle, more when reading/writing, and even more when spinning up. This means it’s impractical to spin up the drive, take a couple of shots and shut it down again; all shots have to be taken and stored in one go, and even then the camera’s battery will last a pitifully short length of time. Fragility and reliability are also a major concern. The moving parts and extremely tight mechanical tolerances to which hard drives are built make them inherently less reliable than solid-state media. With the resolution of still digital cameras increasing apace and the emergence of digital video cameras, the need for flexible, high-capacity image storage solutions has never been greater. In 1999 Iomega launched an innovative removable storage device intended for use in digital cameras as well as notebook and handheld devices. The battery-powered Clik! drive supports the PC Card interface and provides a capacity of 40MB on its 10g, 50x50mm media. It comes complete with an adapter, allowing the transfer of images from CompactFlash and SmartMedia cards to its significantly cheaper 40MB magnetic disk media. The following year Agfa’s ePhoto CL30 Clik! became the first digital camera to use Clik! disks as its primary mode of storage. Mid-1999 also saw...

Hard disk (hard drive) construction

Hard disks are rigid platters, composed of a substrate and a magnetic medium. The substrate – the platter’s base material – must be non-magnetic and capable of being machined to a smooth finish. It is made either of aluminum alloy or a mixture of glass and ceramic. To allow data storage, both sides of each platter are coated with a magnetic medium – formerly magnetic oxide, but now, almost exclusively, a layer of metal called a thin-film medium. This stores data in magnetic patterns, with each platter capable of storing a billion or so bits per square inch (bpsi) of platter surface. Platters vary in size and hard disk drives come in two form factors, 5.25in or 3.5in. The trend is towards glass technology since this has the better heat resistance properties and allows platters to be made thinner than aluminium ones. The inside of a hard disk drive must be kept as dust-free as the factory where it was built. To eliminate internal contamination, air pressure is equalised via special filters and the platters are hermetically sealed in a case with the interior kept in a partial vacuum. This sealed chamber is often referred to as the head disk assembly (HDA). Geometry Typically two, three or more platters are stacked on top of each other with a common spindle that turns the whole assembly at several thousand revolutions per minute. There’s a gap between the platters, making room for magnetic read/write head, mounted on the end of an actuator arm. This is so close to the platters that it’s only the rush of air pulled round by the...

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