Susan Moyse, Consultant, InfoTrends Research Group, Marshfield, MA

Two factors influence file sizes most: bit depth and resolution. Bit depth is most often set at 2 bits for binary scanning, 8 bits for grayscale or 24 bits for color capture. As you add bit depth, you are effectively collecting more information per pixel and therefore increasing the file size.

Resolution is the next metric that you can use to control file size. Resolutions typically range from 100 dpi to 300 dpi in most document imaging applications, but can go as high as 600 dpi in unique cases. As the resolution increases, so will file sizes.

The most important issue is capturing the information on the page so that it is usable. Start by identifying whether you need binary, grayscale or color capture. Then apply the lowest possible resolution that produces acceptable results. A rule of thumb: binary scans typically need a higher resolution to generate adequate results (200+ dpi), while grayscale and color scans can produce good quality results with lower resolutions (try starting at 100 dpi). Try scanning your documents at different bit depths and resolution settings to gauge the effects on image quality and file size.

Harvey Spencer, President, Harvey Spencer Associates, East Northport, NY

The quickest and easiest way to reduce the file size of any image is to scan or save it at a low resolution (measured in dots per inch). Of course, the lower the resolution of a file, the less readable it is. Most document management systems expect TIFF images to be at least 200 dpi, and typically optical character recognition software requires 300 dpi to properly read letters. After lowering the resolution to the extent that you can, you can reduce the size of a TIFF Group 4 image by running a despeckler, eliminating unneeded backgrounds (for instance the pink background color on a form) and deskewing the image. All these efforts will improve the "run lengths" of white areas (a run length is a line of black or white pixels), which is what TIFF Group 4 is optimized for.

In the case of JPEGs, which contain tonal information (grayscale or color), the resolution can often be lower than that set for bitonal images — so you might consider creating 150 or even 100 dpi images. If you reduce the number of shades, you will often reduce the file size. You can even drop out unnecessary shades. Finally, you can adjust the [compression] quality factor — a factor of 75 percent will usually provide an adequate JPEG image and a small file size.