A modern digital camera is considered as „ready-to-use“, and, theoretically, you can take it out of the box and immediately begin to create your masterpieces. Unfortunately, the reality is not so brilliant. One of the first things that you will notice is the volume of the memory card supplied, in this case size does matter. As a rule, it is only enough for testing and has space for measly 10-15 shots. Far too few for full-on fun, another chance for you to open your wallet.

How many memory cards do you need? It depends on several things:

-         sensor size (a 10 Mpix camera creates bigger image files than one with 3.2 Mpix)

-         file format (usually JPEG is relatively compact, but when you prefer RAW, prepare to pay out much more money for extra cards)

-         for casual photographers, a pair of memory cards may be enough, but for professionals not.

In this table you can see an approximate number of JPEG images with “highest” quality that can be stored on a memory card of a given size.

Pay attention: the exact number of images depends on your camera. Even cameras with the same sensor size can create files with a different volume.

You can reduce “image quality” and dramatically improve the number of images, but it is a bad idea: you will get a lot of small-sized, blurry shots.

How much space do you need? If you have a compact point-and-shoot camera you may be able to get by with one 1GB card. At this moment in time such card costs about US$10-15.

Personally, I prefer to carry two smaller (say 512Mb) cards instead of one 1GB card, because I’m wary of putting all my eggs in one basket. On the other hand, you can carry a number of huge 4GB cards to hold your extraordinary output of digital images. It's a question of taste. 

But memory cards are not just about capacity. The next parameter that should concern you is speed.

Memory card speed refers to how fast the card can write (store) and read (play back) files. Generally, faster cards will allow you to shoot images and play them back faster than what’s possible with a slower card. But before you go out and buy the fastest (and most expensive) card on the shelves, consider the kind of camera you have and what kind of pictures you take with it. Some cameras don't have the internal circuitry to take advantage of fast cards, and using a faster card in a slower camera is a waste. In those cases, it's better to save a few bucks and buy a middle-class card.

As a rule you need extra-fast cards:

-         for use in DSLR cameras

-         for using RAW-files

-         for shooting fast events like sports when you will be capturing a lot of photos in a short time

And, naturally, when your camera can’t work on very high speeds at all (refer to your user manual), there is absolutely no reason to purchase hi-end media.

How we can define “fast” or “slow” cards? As a rule you can find the necessary information on the packaging.  Some manufacturers use the same “X” notation, like you see on CD drives. “1X” speed means 150 Kbytes/s, and, for example, 60X means 60x150=9000 kBytes/s or 9 MB/s. Or you can search for absolute values on a package or manufacturer’s web-site. “Write” speed is more important, because when playing back you can usually wait a bit.

At the moment the fastest SD-card on the market has “133X” or 20MB/s. and the cheapest card provides “23X” or 3.5 MB/s.

Some words of warning about card usage. Usually memory cards are robust and their misuse is difficult (but, as usual, some guys are able to do it).  The main problem that can happen to your memory card is to lose it.

Other rules are very easy:

-         never twist a card

-         never get a card wet

-         never try to open a card

-         the contacts should be clear.

For these reasons it’s better to use special cases to store the card when it is not in either a camera or a card reader. The case protects it against all of the above. You'll never regret the few Pounds, Bucks or Euros you invested in a card case.