"How To" Guides > Scanning Images
Scanning Photos and Documents
How Much Pixel Resolution Do You Need for Scans?
If you are not yet comfortable with the concept of pixels and their impact on print quality, it may be useful to read our article on Digital Image Basics. The number of pixels you need to capture in a scan is largely dictated by one of two scenarios.
You know the pixel needs for a specific project
If you know exactly what your scan will be used for, and you are confident in the digital math relationships between pixels, aspect ratios, cropping needs, and print quality, you can simply scan to your needs. For example:
► If you are scanning images that you are confident will only be printed at or below the size of the original, a scan at 300 pixels per inch (PPI) should be adequate, as these images can then be printed at professional print quality resolution of 300 PPI.
► If you are scanning images for website insertion or email attachment, the images will be displayed on a monitor. Therefore, a scan at 300 PPI is also adequate, and will likely result in an intentional or default downsizing/resizing of the image for monitor display.
► If you plan to print enlargements and/or crop the scanned images, you should target a pixel capture resolution that provides in the range of 240 to 300 pixels per inch of print when possible.
You desire pixel flexibility for future unspecified projects
If you are scanning for archival preservation purposes without a clear future usage in mind, the goal is then to balance file size with future flexibility. In this case, we recommend that you:
► Routinely scan common size photo prints at 600 PPI and save the files in Jpeg at the lowest compression and highest quality settings. This provides you with the flexibility to double the size of the image in a print enlargement while maintaining a 300 PPI professional photo quality print resolution or up to four times the size of the original at a still respectable 150 PPI.
► Slides and negatives should be scanned at much higher PPI settings, in the range of 2000 to 3000 PPI, as the original media is smaller than a typical print, and this order of resolution should provide you with high quality prints of up to 8" x 10".
► Scans of text documents or other black and white images that are more suitable for the Gif format can successfully be scanned using default scanner or software settings for a black and white document.
► Explore the available settings on your scanner and image editing software, and experiment with various settings. Menus and choices can be intimidating at first. However, the actual choices are few and easily learned. Many default settings are adequate, but can be improved with a little knowledge and practice.
Tip / Hint: Many digital equipment manufacturers are marketing ever increasing levels of resolution capability, and most have reached levels of diminishing returns. Many moderate priced flatbed scanners can now capture 4800+ PPI. However, capturing more resolution than you need only slows the scanning process and creates larger files. If you are comfortable with pixel math, and have a good handle on your future uses, you can save a lot of time and storage by scanning to your specific needs rather than pressing the excess capabilities of your equipment.
