Most digital cameras use removable cards to store your images until you are ready to download them to a computer, your printer, or a photo printing kiosk. Although there are a number of different types of cards including MMC, XD, Sony Memory Stick, Mini & Micro SD, and for older cameras Smart Media cards, I’m going to specifically deal with the two most popular types – the Compactflash, the Secure Data (SD) & its high capacity version called, appropriately enough, a Secure Data High Capacity (SDHC) cards. Much of this information will apply to any card type.
Although neither type of card is inherently better than the other, with few exceptions, the user doesn’t have a choice – the manufacturer of the camera picks one or the other and builds in a slot & connector that only works with one type. As of today, the CF cards have a higher capacity, but who knows what the future will bring.
Most camera manufacturers include a card with the camera, however the included card will often be of limited capacity. Camera owners have a wide range of choices when purchasing a new card. The obvious choice is to purchase an exact duplicate of the card that came with the camera; less obvious are the choices of card manufacturer, size, and speed. Depending on the card type, cards are available from as small as 512MB to as large as 100GB (although a 100GB CF card will cost more than most cameras). More typical sizes today run from 1GB to 16GB.
If we start with size, one school of thought is the larger, the better. After all, the larger the card, the less often you will need to download the images from your camera, and the less likely you are to run out of space at an inconvient time. There are problems with this approach. First, you are putting all your eggs in one basket. Although both types of cards are quite reliable, sooner or later you will have a failure, often caused by accidently formatting a card, erasing the images. The larger the card, the more images you will probably have stored on it & the more you will lose with a failure. Although there are recovery programs ( I have used PhotoRescue – $29.00 & Sandisk’s RescuePro – Free with some CF cards & $40.00 if purchased alone) recovering images from cards is a long & often painful process. Another problem with large cards may be the limit of your camera’s operating system. Some cameras will not format a card larger than 2GB, others may be limited at 32GB. Before spending the extra money for a large card it is worth checking your manual or the manufacturer’s website for the maximum card size the camera supports. If you are purchasing very large cards you will pay a premium. For some cards it will be less expensive to purchase 2 cards that add up to the capacity of one large one.
How large a card should you use? I prefer to limit my card size so that it holds less than 100 images at the largest file type I generally use. The card size that determines this is dependent on the size of your average image size. A 3 megapixel camera could produce a jpg image file as small as 500KB or a TIFF as large as 18.9MB. A new Nikon D3x with a 24.5 megapixel sensor produces a 50MB RAW file. Obviously, the larger the file size the larger card will be necessary to hold 100 images. If you plan on taking more than 100 images before moving the images to more permanent storage, purchase multiple cards & change them as they get close to full, much like you did with film cameras.
Another variable for most types of storage cards is speed. Almost all cards have both a write & read speed. Depending on your camera & the method you use to download images to a computer, card speed may be an important choice. In most cases, the faster the card, the more expensive it will be. There is no advantage of purchasing a card that has a write speed faster than your camera is capable of writing to it. In the case of read speed, the advantages of faster cards depends on how you read the card.
Very few camera manufacturers give card speed specifications in their manual, although some do include the information under specifications. A better approach is to check camera reviews at places such as dpreview or Digital Camera Resource Page. You might also check Robert Galbraith’s pages on his website that compare the performance of CF & SD cards in different cameras.
In most cases, connecting the camera directly to your computer will be the slowest method of downloading your photos. The advantage is you don’t have to remove the card. There are card readers that can be plugged into a Firewire or USB computer port as well as adapters that allow cards to be connected to a laptop through a PCMCIA or Express Card Slot that will read cards faster than the connection directly from a camera. Are they necessary? It depends on how fast you need the images, how long you are willing to wait for a download & how long you are willing to have your camera unusable while it is downloading the images. One note – the card readers, as well as the ports on your computer also have speed limits – be sure you don’t combine an expensive fast card with a slow reader…
A last variable is the card manufacturer. The major manufacturers are SanDisk & Lexar, however there are many other suppliers, often selling cards just as large & fast for less. The previous link is to My Digital Discount, a low cost supplier of almost all brands of cards. Some camera manufacturers only recommend cards from the major manufacturers; meaning those are the only ones they have used in tests with their cameras. In most cases the less expensive cards will work fine, however there does seem to be more reports of card failures with the least expensive brands. The choice is yours.
One last point – if you use multiple cards, and I feel this is the best solution, be sure to develope a procedure that keeps track of empty verses full cards. Although your camera will not let you overwrite images that are already on a card, putting a full card into the camera doesn’t work very well, and if you are in the habit of formatting a card as you place it in your camera (a good idea) you obviously don’t want to do that to the card you removed earlier in the day, at least not before you have downloaded the images to your permanent storage! I keep empty & full cards in a different pocket im my camera bag, or, if working without a bag, a different pocket.