With analogue cameras the film records and stores image while with digital cameras, separate devices execute these two functions. The image sensor captures the image then it is transferred to a storage device within the camera. Since the modern digital cameras have high image resolution of about 15 megapixels and produce image files of size up to ten megabytes. The storage of such images requires compact storage media of enough capacity. Basically, it is unrealistic to put DVD, CD, or hard drive into a digital camera, because of either power consumption or size. As a result, a unique media storing device was created (memory cards or flash cards). Flash cards or memory cards employs non-volatile memory chips to store images. This device stores images temporally since at a point you will have to transfer the data into the computer, erase the device and re-use it.
All the current digital cameras use some form of removable storage devices- flash card (memory cards) or at times small hard disks. The total number of images one can store during a photo shooting session will depend on a number of factors but not limited to:
The file format or resolution used to capture images
Compression size used
The capacity of the storage device expressed in gigabytes, megabytes or kilobytes.
Knowing the maximum number of images your device can store is essential because once the limit is reached, you must move the images to a computer, or laptop, erase the images to create room for new pictures.
Over the last few years different types of flash cards have appeared and disappeared. Currently there are two common types used. Secure Digital (SD) and Compact Flash (CF). These memory cards store image files on flash chips that are same as the RAM chips in the computer; however, there is one notable difference. The taken pictures are retained ad infinitum with no power to the card. These chips are usually packaged in a case having electrical connectors. This sealed unit is known as card. Flash cards or memory cards consume small amount of power, occupy small space, and are very strong. Besides, they are convenient and you can carry several of them and change them as required. The digital camera storage cards include:
Memory Stick™–this property format is from Sony Company. It has a stick of gum shape and mostly used in Sony products.
CompactFlash (CF) – this flash memory was made by SanDisk Corp and have size same as that of matchbook.
Hard drives- such as Sony’s compactvault and Hitachi’s Microdrive are usually high speed and capacity hard disk drives. These hard drives are so meager that you can plug them into the slot of a type II compact Flash on a flash card reader or digital camera. It is important to note that the slots of type I Compactflash are thinner.
Secure Digital (SD) – these cards have smaller sizes than CompactFlash cards and are used in more than one half present camera models. However, some compatibility issues is noted because the latest 2GB and larger cards appear similar as older cards, but employ Secure Digital High Capacity (SDHC) format that is not present in the older cameras.
One-time use flash cards. These have been introduced because they are cheaper than flash memory. However, they are not ideal for serious photographers.