Choosing the Right Resolution When Scanning Images

Scanners are great tools for converting images from prints, negatives, and slides into a digital form for the purposes of storage, editing, and sharing via the internet or to produce actual prints. The quality of the images from a scanner depends in large part upon resolution. Some scanners offer significantly higher resolution than others but most allow the user to adjust the resolution used for any given scan.

Because higher resolution means more detailed and higher quality images why would a user ever select to lower resolution? There are actually a couple of reasons why someone might decide to adjust the resolution downward when scanning.

One reason that the choice to use lower resolution would be considered is that higher resolution images contain more information. The downside of more information is that file sizes are much larger, requiring much more storage space. When storage space is limited, higher resolution images can be a drawback. Users must experiment to determine what level of quality they are willing to accept in order to preserve memory.

In addition to the increased storage needs, the larger file size of high resolution images creates a second drawback. Such images are slower to scan, manipulate, and download. A user may not wish to spend exorbitant amounts of time dealing with larger file sizes and those receiving or waiting for a web page to open that contains such files may become impatient with the process as well. Again, the user has to determine how much image quality they are willing to sacrifice to get smaller files that save time.

Determining what resolution to use when scanning can depend on a number of things: the type of material being scanned, the quality of the image, and how the resulting file will be used.

Slides and negatives require a higher resolution than a print. Because they start off quite small, they will likely be enlarged for viewing purposes. When any image is enlarged, greater resolution is needed to maintain acceptable image quality. The number of pixels or bits of image information needed for the enlarged image to be of reasonable quality may need to be 2,000 or more.

If an image being scanned is a text document less information will be needed to create a clear image and, indeed, a resolution of only 100 should be sufficient. If the image scanned is a picture that will be shared only via computer, then a resolution of 100 or so may still be quite acceptable as the resolution at which a computer screen is able to display is generally limited. However, if that same image will be printed, resolution will need to be greater; perhaps 300 to obtain an acceptable image. Just as explained when scanning slides however, if a user chooses to enlarge that same image, greater resolution will be required to maintain quality. For instance, if a 4x6 print will be scanned and enlarged to a 10x15 print, then a resolution of at least 600 would be wise.

Clearly, scanning images at the highest resolution can create optimum image quality but when speed of scanning and downloading are important or storage space is limited, users are wise to consider adjusting resolution downward in situations where acceptable image quality is possible with lower settings. Some experimentation will be required to find the level of image quality that is acceptable to an individual user.