Resolution is how many dots per square inch or pixels per square inch a RASTERIZED image has. It is a form of measurement most commonly referred to as "DPI" or "Dots Per Inch" The simple equation for finding what resolution to scan or digitize an image at is 2 X LPI at actual size = Resolution. (LPI is an acronym for Lines Per Inch. At Williams we use 150 LPI for printing and 75LPI for Large Format Digital Prints). For Williams Printing & Office Supply it would be 300dpi at actual size for PrePress/Printing or 150dpi at actual size for Large Format Digital Prints. If your picture you are scanning is smaller than what the final size it needs to be then multiply the target resolution X the percent of enlargement (convert percents to decimal - Target Resolutions are 300dpi at actual size for printing, 150dpi at actual size for Large Format Digital Prints) to find the final resolution needed to scan or digitize your image. Example: a 3X5 photo needs to be 6x10 and printed on a press. So you would enlarge it by 200% or 2.0 - So take 300dpi and multiply it by 2.0 (200% in decimal format) and you would get 600dpi as a final resolution. Now when you enlarge an image you are reducing resolution so a 600 dpi image at 3X5 would end up being 300dpi at 6X10.