Sidebar: May DCP

Nowadays, very few digital cameras have any built-in or fixed internal memory for the storage of digital images; instead most digital cameras have internal spaces or slots to accommodate tiny rewriteable memory cards. These come in various physical forms (e.g. Compact Flash, SD, MMC, Sony Memory Stick, XD, etc), speeds and capacities (now 8Gb capacity cards are available!).

Storage Capacity

The number of images any particular memory card can store depends on its capacity and how large the individual digital images are. The image size depends upon various factors including how many megapixels your camera’s internal light sensor has, what resolution and file type you set in the camera’s preferences (e.g. small JPG file, normal JPG file, fine JPG file or High JPG file or RAW format), whether you take the photos in greyscale or full colour, and finally, how much detail there is within the image (large areas of blue sky don’t require as much information as more complex parts of an image such as grass or trees, etc).

While the memory cards used in digital cameras are very practical and compact, there are two important reasons why they are not appropriate for long-term storage or archiving. Images saved on a memory card may well remain stored safely for several years without degradation or loss but these cards should not be considered as highly secure forms of storage. Also when compared to the low cost of a blank writable CD or DVD disc or the cost per megabyte of todays huge capacity hard drives, memory cards are much more expensive forms of storage.

Memory cards can have different “speeds” which means some can have data written to them by a digital camera and read from them by a computer at a much higher speed than others. Having “fast” (and more expensive) memory cards is of most value when you own a digital single lens reflex (SLR) camera, which usually have larger image sensors with high megapixel counts. These cameras therefore create larger images files which need to be written to the memory card as quickly as possible so that there is minimal delay until the camera is ready to take the next picture. And even if your camera’s internal data transfer speed isn’t a match for the speed of your memory card, you will still benefit from a faster upload speed from the card to your computer!

As a general rule, it’s useful to have several memory cards so that if one card fills up it’s a simple matter to quickly remove it from the camera’s memory card slot and pop in another one to allow you to continue taking pictures. You can transfer the photos from the card at a later date and then “reformat” or erase the full card to free it up for further use. Each card is good for perhaps as many as 100,000 reuses before it deteriorates and needs to be discarded. Of course there will always be some cards which “die” prematurely for unknown reasons! The good news is that the price of memory cards has dropped dramatically in the past few years and they will continue to get cheaper while their storage capacity rises almost as quickly!

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