By Richard Heller


This past week, I received e-mail from a person who had just purchased a scanner and was having a problem. It seems that every time he scanned an image, he was receiving an “out of memory” error. This error message was not entirely true; what he actually had was an error caused by running out of space on his hard drive.

When you scan an image, you select a resolution that you would like to use. Of course, you bought one of those 600 or 1200 dot per inch (dpi) scanners so that you could get those 75-year-old photos with all the lines and scratches into your family tree. The problem is that the higher the resolution that you scan, the larger the file that you create will be. An 8 1/2” X 11” page will be 419 megabytes when scanned at 1200 dpi. At 600 dpi, the size drops to 105 MB, while at 150 dpi, it’s only 6.5 MB.

Since most people don’t have 512 MB of RAM in their computers, the image is saved to the hard drive as it is being scanned. Depending upon the speed of your computer, it may not be able to write the file to the hard drive fast enough, and this will cause the scan to fail or the computer to freeze up. If you are scanning a number of images, you will need 400 MB on your hard drive for each image you scan; five images will take up 2 Gigabytes of hard drive space. You will also need an additional 400 MB of space available for the image as it is being scanned, as it is placed in a temporary file until you tell the program to save the image; then the temporary file is deleted.

By lowering the resolution to 150 dpi, the image will fit in memory as it is scanned and will only take up 6.5 MB on your hard drive. Those same five images will only take up about 30 MB of hard drive space. You will discover that you probably won’t see much difference when viewing the image on screen or in your printout when the image is scanned at the lower resolution.

As a guideline, it is recommended that you scan at 125-225 dpi when scanning for a newspaper, 200-265 dpi for a magazine, and 225-300 dpi when scanning for an art book. The higher resolutions of your scanner are useful if you have an adapter to scan in photo slides.

One thing you may discover about your scanner is that the resolution stated on the box may not be quite the truth. There are actually two resolutions that your scanner has–an optical resolution and an interpolated resolution. The difference between the two is that the optical resolution is what the scanner actually scans at, while the interpolated resolution is done by software that adds extra dots to the scan in order to create a better image.

Richard Heller is an independent computer specialist who specializes in repairs, installation, upgrades, technical support, Internet sharing, data recovery and diagnostics. If you have any computer or service-related questions, please send them to The Rock River Times or e-mail

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