It can be one of the most frustrating experiences in photography: Suddenly a perfect opportunity for a picture pops up and you press the shutter button and the camera beeps an error message: "Memory Card Full." Knowing how many pictures a memory card holds is the key to avoiding disappointing situations like this.
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Determining Image Size
The number of pictures a memory card can hold depends on the size of the pictures being taken. A two- to four-megapixel image will take up about one megabyte on a memory card. A five- to six-megapixel image will take up about two megabytes. A seven- to eight-megapixel image will take up about three megabytes. A nine- to 10-megapixel image takes up a little more than three megabytes. Knowing this, you can divide the available memory by the amount of megabytes your pictures will take up (considering how many megapixels each has).
256MB Memory Sticks
A 256MB memory stick can hold approximately 250 two- to four-megapixel images, 120 five- to six-megapixel images, 85 seven- to eight-megapixel images, or 60 nine- to 10-megapixel images. These numbers will vary slightly depending on the types of pictures being taken because the amount of memory each picture takes up varies slightly.
Many cameras with eight or more megapixels offer a setting that allows you to take pictures at less than full resolution in order to conserve space on the memory card. For example, at low resolution, the camera might only take a two-megapixel image instead of using its full, eight-megapixel capacity. While this will mean that more pictures can be held on the card, the drawback is the pictures will be lower quality. With memory card prices dropping quickly, it is usually better to invest in a larger memory card if the current card is filling too quickly.
Many memory cards advertise themselves as being "high speed" or "extreme" because of the faster writing speeds. These cards can be misleading because they will not increase shutter speed, decrease shutter lag, or speed at which the camera takes pictures further than its built-in capacity. Many times, point-and-shoot cameras do not have the capacity to take advantage of the faster data writing capabilities of these cards. Most DSLR cameras have the picture-taking speed to take advantage of this so they can take more pictures in a faster burst.
Some cameras today allow video to be taken as well as still images. At 640 x 480, a 256 MB memory card could take up to two minutes and 56 seconds. If the video is shot at a lower resolution--320 x 240--it would take around 10 minutes and 56 seconds. Both of these numbers assume 30 frames per second.