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Chapter 4. Dealing with Digital Camera F... > Image Size, File Size, and File Comp...

Image Size, File Size, and File Compression

You can adjust the image size, file size, and image quality of your digital camera images. The guidebooks and manuals don’t always make it clear that these adjustments are three entirely different things. However, image size affects file size and image quality, and image quality affects file size. File size, while it’s dependent on the other two, has no direct effect on image size or quality. No wonder it’s confusing! It’s a good idea to get these three terms sorted out before we move on, so that we’re all talking about exactly the same thing. Here’s a quick summary:

  • Image size is the dimensions, in pixels, of the image you capture. For example, if you have a 5MP camera, it might offer a choice of 2560 × 1920, 1600 × 1200, 1280 × 960, and 640 × 480 resolutions. Each reduction in resolution reduces the size of the file stored on your memory card. A TIFF file at 2560 × 1920 pixels might occupy 4MB; a 1600 × 1200-pixel image, 1.7MB; a 1280 × 960-pixel image, 1.3MB, and a 640 × 480-pixel image, less than 1MB.

  • Image quality is the apparent resolution of the image after it’s been compressed and then restored in your image editor. The TIFF format can compress the image, somewhat, with no loss of image quality, but JPEG compression does reduce the image quality for reasons that will become clear shortly.

  • File size is the actual space occupied on your memory card, hard disk, or other storage medium, measured in megabytes. The size of the file depends on both the image size (resolution) and quality/compression level. You can reduce the file size by reducing the image size or using a lower-quality/higher-compression setting.


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