Memory Cards

Memory cards are the system that digital cameras use to store any images that have been taken. When you take a picture, it is recorded by the camera's sensor and stored on a memory buffer. This is a fixed amount of memory that is built into your camera, and it can process information very fast. As soon as the picture goes into the buffer, it is sent to the memory card for permanent storage. The memory built into a digital camera is not permanent; only the memory card is.

Different manufacturers use different memory card systems. They all do the same job, but generally only one type of memory card will fit in a particular camera. Some cameras can accept more than one type of memory card, but these are the exception, rather than the rule. Different memory cards available include: Compact Flash - type I & II (CF), Secure Digital (SD), Sony Memory Stick (and Memory Stick Duo) and XD memory.

If you already have a substantial quantity of memory of a particular type, then your choice of camera may be influenced by those that will accept the memory you already have. Otherwise, your choice of memory will be dictated by the camera you purchase.

Memory cards can be purchased in different sizes (memory size, not physical size) Commonly available sizes are: 64, 128, 256, 512, 1024 and 2048 Mb. The latter two sizes are more commonly known as 1 and 2 Gb cards respectively.

The table below displays the number of images taken from a 5 megapixel camera that can be stored on memory of different sizes:

The actual number will differ depending on the content of the pictures. It follows that if your camera has fewer megapixels you will be able to store more images and vice versa.

Once you have decided on the amount of memory you want to buy, you need to consider the speed of memory card you require; how fast can it read and write data. This is not really a concern, unless you are an enthusiastic photographer taking many photographs in quick succession, you have a camera with a large megapixel count that creates large files or you plan on using your camera's video function to take long video clips. In all of these situations, a fast memory card is beneficial as it will allow the camera's buffer memory to remain relatively empty. If the buffer memory is allowed to fill, you won't be able to take any pictures until it has cleared.

The speed of a memory card is designated by a number followed by a multiplication sign; for example 32x. This means that the memory card has a minimum write speed 32x faster than a 1x memory card has. Which is no good whatsoever, unless you know that 1x refers to 150KB/second of data transfer. So, a 32x memory card can store data at a rate of 4.8MB/second (150x32). For reference, 1MB (megabyte) is equal to 1000 KB (kilobyte).

Another consideration is the reliability of your memory card. The last thing any photographer wants it to fill a memory card with pictures and then have that card fail.

Many manufacturers offer premium products with longer guarantee periods, and it might be worth considering one of these products.

As a final point, some people prefer to have several small memory cards, rather than one large capacity memory card. The logic behind this is that if you are using them and one fails, then you will still have pictures on a number of other cards and your photo-taking session won't have been a complete waste of time. The down-side of this is you will have to frequently replace memory cards, and this might interrupt your shooting and may cause you to miss an important shot.

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