The Digital Dungeon

DPI (Dots Per Inch) in digital imaging means how many pixels per square inch make up the image. For example, if I scan a 1 inch by 1 inch piece of paper in 300 DPI, then there are 300 pixels in the image that I scanned. If I looked at the digital image and realized that it did not show enough detail of the image, then I would scan it at 600 DPI. Now, the digital image has 600 pixels that represent the image. You can keep going up and up, but there reaches a point where adding more pixels does not gain you any more detail. Why? Because at some point you start picking up detail about the paper (or medium) that the items is on. You start to see the fibers in a piece of paper, or the dimples on it’s surface. Once you start picking up that level of detail, you are actually creating more “noise” in the image than is necessary and you need to back off on the DPI. Most printed text, for example, is printed in 80-90 DPI on a page. However, this does not mean you can scan the image at ...

File Formats What format you use is dictated by your goal. Libraries have a tendency to want to have a small access copy of reasonable quality, and a high quality archival copy of reasonable file size. To get a better idea of what the different formats are, and what they do, I've linked to some articles: TIFF (Tagged Image File Format ) JPEG JPEG2000 PDF JPEG is the perfect format for full color or grayscale images because it provides a nice balance between quality and file size. The format is stable as long as you do not edit the file over and over. If you are going to be editing the file, save it as a Tiff first, then save it as a JPEG. JPEGs are perfect for access copies, and sometimes for Archival copies. A full color or grayscale Tiff is huge as far as file size goes. A black and white Tiff, however, is generally smaller than a black and white JPEG. Don’t ask me why. Tiff also provides the best quality and stability. You can use Tiffs for archival storage if you have a...