Digital cameras are seldom supplied with memory cards these days, partly because the cards that were once supplied are woefully inadequate for today’s camera resolution levels and partly because many digicams come with built-in memories where pictures can be stored.
|[Click here for updated information on memory card speeds and capacities]
How Much Memory Do You Require?
Some cameras have dual slots that will accept different types of cards. With more sophisticated cameras it is usually possible to transfer image files between cards and decide which card
How Many Images Can You Store?
The actual number of pictures that can be stored on a card will depend on the camera model and how much the JPEG files are compressed. Some cameras apply higher compression ratios that others. Card capacities will be significantly higher when lower resolution/quality settings are used.
Photographers who use DSLR cameras will find they need higher storage capacity – especially if they shoot raw files. For this reason, we recommend at least a 1GB card. The table above gives the approximate capacities for high-resolution JPEG files at a compression ratio of 1/4 from typical DSLR cameras.
Compression ratios vary for raw files, although all manufacturers provide lossless compression. For example, 10-megapixel raw files can range in size from 17.66MB to 9.8MB, depending on the file format used and the degree of compression applied. TIFF files, which are usually uncompressed, are roughly three times the resolution of the camera’s sensor in size (e.g. around 30MB for a TIFF file from a 10-megapixel camera).
How Much Video Can You Store?
Factors Affecting Card Capacity
1. How the computer operating system sees it. Most operating systems define a megabyte as 1,024KB (1.024MB), which means a 1GB card’s capacity is 1,048.576MB.
The last two factors together explain why the actual capacity of most memory cards is slightly lower than it might appear.
How Much Memory Do You Need?
Travellers without laptops or portable storage should have at least 4GB of memory card capacity with them and allow a minimum of 2GB per day when they will be in transit and unable to transfer their shots to optical disks. You should be able to find services that will transfer images from a memory card to a CD or DVD in most population centres. We recommend purchasing two copies of each disk: one to keep with you and the other to send home as a back-up (in case the other disk is lost or damaged).
Do You Need a High-Speed Card?
Memory card manufacturers charge premium prices for their high-speed cards but, for photographers who shoot with digicams, fast cards will be of little benefit. Even many DSLR photographers will find standard 40x speed cards will be adequate for most shooting situations. However, they will make a difference in how long it takes to download files to a computer, particularly if you have a fast PC.
High speed cards are also worthwhile for video recording, especially if your camera or camcorder supports the new, ultra-fast UDMA technology (which will be supported in the next generation of DSLR cameras). However, you need a UDMA-enabled reader to benefit from the speed advantages this technology offers when downloading large files to a computer.
The main determinant of memory card speed is how the controller in the card exchanges data with the camera. This can vary by as much as 3-4 megabytes/second from one camera to another. The flash memory itself also determines the maximum speed of different cards and accounts for a sizeable part of the price premium charged for fast memory cards.
Is it worth paying more for a high-speed card? It is if your camera can match the card’s data transfer speed and if you use burst mode frequently. If you take shots one at a time, the speed of the card is irrelevant.
High-speed cards may also be worthwhile if the camera is unable to shoot and write simultaneously, or if your camera’s innate write speed is slow and its buffer memory is small. Otherwise, you may not notice much difference between a high-speed card and a standard one.
Memory Card Tips
Treat memory cards with care. Keep them in dust- and water-proof cases while they are not in use. Always carry at least one back-up card in case you run out of memory on a shoot.
Don’t open the camera’s card compartment while the files are being written; it will almost certainly cause shots to be lost. Shots may also be lost if the battery fails while files are being written. In most cases these ‘lost’ images can be recovered with file recovery software (which is supplied with some high-speed, high-capacity cards). Many camera shops provide a file recovery service for a small fee.
Always format each card in your camera before you use it, making sure you have transferred the images it contained to an archive folder. Some digital cameras can’t operate with cards that were formatted in a computer or a different camera.
Don’t expect a camera to display images captured on a card by a different camera – even if it comes from the same manufacturer.
For other memory cards, write protection can be applied through your camera’s play or set-up menu (indicated by a tools icon). The function is usually indicated by a horizontal key icon. The same menu is used to remove write protection.