Compared to film photography, digital certainly has its conveniences, but choosing the right memory cards may not be one of them. There are around 20 different formats, at least 10 levels of storage capacity, multiple write speeds and other variables on top of those. Several quick steps, however, will show you how to buy memory cards for a digital camera.

The flash memory card has replaced film as the primary storage device for photos, but there's more to choosing the right card than knowing the proper format for your camera. Depending on the camera and the card, you might be able to store either 12 or 700 pics at once; snap 20 shots in rapid succession, or have to wait around after each one.

• As with film, the formats of memory cards differ in size and are not interchangeable. Attempting to use a Compact Flash card in a camera that takes Memory Stick would be like trying to jam a roll of 35mm film into a 110 camera. Before buying memory cards, you'll need to find out which format is compatible with your camera.

1. Consult your camera's manual.
   • The card format should be secified in a section titled "memory card compatability" or "storage."
2. If you cannot locate the manual, look on the cap of your camera's memory card slot.
   • You should find an insignia specifying the card format. The most common are:
     • CF (Compact Flash)
     • SD (Secure Digital)
     • xD (Extreme Digital)
     • MS (Memory Stick)
     • MMC (MultiMediaCard)
     • SM (Smart Media)
   • Keep in mind that most of these categories have subformats, such as Mini SD and Memory Stick Micro. If you see a notation that you don't recognize, look it up online.
3. If you can't discern the format from the camera itself, go to Digital Photography Review's database of over 1000 cameras models.
   • Select your camera's manufacturer and then the individual model.
   • Scroll down to the row marked Storage Types and note the specified format.

• A roll of film can store as many pictures as the number of exposures it contains, but memory cards are less clear cut. The exact number of images a card can store depends on a combination of its storage capacity and the resolution capability of your camera.

1. Determine the resolution capability of your camera.
   1. Resolution is measured in megapixels.
   2. If you can't find your camera's megapixel count in the manual or noted on the camera itself, refer again to Digital Photography Review's camera database.
   3. Record the megapixel count on a piece of paper.
2. Determine the ideal memory card storage capacity for your camera.
   1. Storage capacity is measured in megabytes (MB).
      • A gigabyte (GB) isequivalent to a thousand megabytes.
      • A card with 128MB is a low capacity card, while 16GB is very high capacity.
   2. Go to this storage capacity table.
   3. Find the row matching your camera's megapixel count.
   4. For each column specifying card storage capacity, write down the approximate number of photos that can be stored.
   5. Keep in mind that higher capacity cards can be much more expensive; depending on price, it may be more practical to settle on two or three lower capacity cards.
   6. Note that this is only a rough figure; camera setttings, such as the amount of compression you use to store your images, will affect the exact number of photos per card.

• Write speed indicates the amount of time a card takes to store an image. The slower the write speed, the longer you'll have to wait between shots, but the difference can be negligible.

• If you've ever burned a CD, you may be familiar with figures like 8X or 12X. These are X increments, which note the amount of memory a device can store per second. A memory card's card's write speed is also measured in X increments.
  • 1X is equivalent to 150 kilobytes per second.
  • 4X is considered a very slow write speed.
  • 40X is sufficient for most point and shoot camera users.
  • 150X is about highest speed of any card currently on the market.

• Depending on your camera and the kind of photography you plan to do, you may not see much benefit from a high speed card. A card marked higher than 40X will be of greatest use for the following applications:
  • DSLRs can operate significantly faster.
    • Digital SLRs have high megapixel counts and a larger sensor than point and shoot cameras, factors which increase the amount of data required to store for each image, slowing down the process.
  • Action shots can be made in faster succession.
    • If you want to catch take sequence of an athlete in motion, a high speed card can allow you to make quicker and more frequent bursts of snapshots.
  • Movie mode is enhanced.
    • If you shoot short movies with your still camera, a high speed card will allow you to record more smoothly and for a longer period of time.

• You now have the criteria you need to buy a memory card for your digital camera: the format your camera uses, the storage capacity you need for photos and the write speed to optimize your camera's performance. It's time to buy your cards and get started taking pictures. In order to avoid fakes and grey market imports, your best bet is to buy your memory cards from a well-known online retailer or a brick and mortar electronics store.

• Online Retailers

• • • Tiger Direct
    • New Egg
    • B&H Photo
    • 4AllMemory.com

• Brick and Mortar Stores
  • These retailers sell a broad assortment of memory cards, both online and from physical locations around the country:
    • Ritz Camera
    • Fry's
    • J&R
    • Best Buy