The drawbacks of all bitmapped images occur when scaling to a larger size. As the image is enlarged, curves and edges appear to get rough or jagged. Increasing ppi on a low resolution image still results in a jagged printed image. Before you scan any art, determine the size of the item as it would be placed for output. Standard monitor resolution for Macintosh OS is 72ppi and that of Windows is 96ppi. Images that are used on websites are typically created at monitor resolution and are usually not appropriate for high-resolution printing. All image files or scans intended for printing need to be at a minimum of 225 ppi and no larger than 300 ppi at 100% of final desired size to render them properly for quality print reproduction.

Do a little arithmetic before you scan. If you were to use an image scaled down to 50% of original size, this would double the image's resolution. Scaling a particular image to 33% of the scan triples the resolution, etc. A final resolution of 1.5 times the LPI works well in most cases. LPI stands for lines per inch, and for offset printing the LPI is usually 133 or 150 for printing on uncoated papers and 175 to 200 for coated sheets. Resolution in terms of PPI or pixels-per-inch. Final scan resolution means that you've calculated the change in spatial resolution when you size your original scan, so the formula is: PPI = LPI x % increase or decrease of original x 1.5.