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“I USE a 256MB memory card with my 6MP camera. How many pictures will my card hold?”
We’d love to give you a definitive answer: when shooting JPEGs at the highest resolution and lowest compression settings, your card will hold exactly 150 images. But there are too many variables. Why isn’t there an exact number, as with a roll of film?
“With film, you have a fixed roll length and frame size. With digital, you have a fixed storage capacity, but the frame size varies, and the amount of data that you can store in the area changes,” says John Omvik, Director of OEM and Professional Product Marketing for Lexar. “Most 6MP cameras have two to four resolution settings with three JPEG quality settings. The amount of JPEG compression varies, based on scene content.”
What affects file size?
Scene content: A complex scene filled with detail produces a larger file than a simple scene. A shot with little detail—an overexposed blank wall, for instance—can increase the “shots remaining.” Why? The camera may recalculate the number of pictures to go based on the average file size of pictures already stored on the card.
Image size: Reduce the resolution or number of megapixels used (sometimes referred to as the “image size” setting), and you’ll fit more images on your card. The accompanying chart will give you a rough idea of what to expect. On some 6MP cameras, the actual number of pixels measures 3008x2000; on others, it’s 3024x2016. This can affect file size.
Compression: If your camera has several compression (or “quality”) settings, you can increase the number of images on your card by choosing a higher compression setting. However, doing so reduces image quality, progressively. Also, “medium” compression could create a 1:20 compression ratio on one camera, and 1:35 on another. “Fine,” “Normal,” and “Good” are similarly vague; there’s no standard definition.
File formats: Most high-end cameras feature JPEG and RAW; some have TIFF file formats, plus movie formats on compact and EVF cameras. RAW files are larger than JPEGs. TIFF files, followed by RAW + JPEG, take up the most space. While some camera manuals have charts with approximate capacities, most don’t.
The bottom line: When in doubt, bring more memory than you think you’ll need, and shoot JPEG images set to the finest quality. You can vary settings based on the importance of the scene or storage remaining.
Card Capacity: Size Matters
The numbers on this chart (based on the one in the Pentax *ist DS user manual, one of the best we’ve seen) are just guidelines. Your mileage may vary.
Click to download Cheat Sheet as PDF
-requires Adobe Acrobat Reader
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