Scanning Tips and Guidelines

Typed Documents

Typed pages are typically going to be black and white images so there is no need to scan them in full color, grayscale will do just fine. Scanning in grayscale also makes it easier to make the background a pure white and create better contrast. It is also one third or less the size of the equivalent color image. Scanning resolution also depends on whether you want to OCR the document or just want to preserve an image of it. Typed documents are usually not as important as an image, rather the information that is presented on the page - thus preserving the information is more important than the look. This being the case, the is nothing wrong with using a compressed file format, such as JPG, to store the file. Storing as a JPG will save a huge a mount of space as well.

For advanced users, you can even convert a typed document to 4-bit grayscale and save as a GIF, which typically yields even smaller file sizes than JPG and usually with better visual quality.

For OCR the purpose is to use a temporary image of the document so a computer can convert the image to an actual editable text file. Because the information is transitory, grayscale works great for the color depth and you definitely want a smaller file size so use JPG for the file type. The resolution is higher, however, because the computer needs a good image of each letter on the page.

Document Preservation
Scan Resolution: 150-200 dpi
Color Depth: Grayscale (8-bit) or True Color (24-bit), depending on your desire.
File Format: TIF or JPG

OCR
Scan Resolution: 200-300 dpi
Color Depth: Grayscale (8-bit)
File Format: JPG

Original Photographs

Original photographs are definitely worth preserving, especially since most photographs starting in the 1950s fade over time - especially color photographs. These are the highest resolution scans that we recommend - a full 600 dpi. We also recommend storing the images in the TIF format, which does not loose any detail but also takes up a lot of room. A typical 8 x 10 photograph scanned at 600 dpi in full color stored as a TIF will take about 120 MB.

Color (includes sepia tone)
Scan Resolution: 600 dpi
Color Depth: Full color (24-bit)
File Format: TIF

Black & White
Scan Resolution: 600 dpi
Color Depth: Grayscale (8-bit)
File Format: TIF

Tintypes and Daguerreotype

Tintypes and Daguerreotypes were typically very small, sometimes measuring only 1 inch square. To really preserve these, you should scan at a minimum of 600 dpi but can go higher if you desire. Also, there was no color so scanning in grayscale will save you some space.

Scan Resolution: 600 dpi or higher
Color Depth: Grayscale (8-bit)
File Format: TIF

Artifacts

Pictures of artifacts or artifacts them selves can be scanned for preservation purposes. And for this, the field is pretty wide open to what you want to do with the image. Try and match your usage to one of the above-listed applications and follow those guidelines.

Posting on a Website

Web sites require much smaller images than are typically obtained from scanning. Except for special cases, most images you want to put on the Internet should be about 500-600 pixels in width. If you are scanning a 4 x 6 photograph, you would use between 80-100 dpi. Normally, however, you would want a high-resolution scan done of the photo or image, then resize that image to 500-600 pixels using your favorite graphics manipulation program.

You really only have two choices in file format when posting an image to a website: JPG and GIF. There are differences between the two, each one excelling in a particular usage. As a general guideline JPG is best for photographs, GIF is best for documents.

Digital Cameras & Megapixels

Digital cameras are very popular now and many people are using them instead of traditional film cameras. Digital cameras, as a general rule, always store their images a JPG (meaning they are compressed and some information is lost). But the tradeoff is you can fit many times more JPG files in your camera than you would in an uncompressed format.

Megapixels is a measurement, undoubtedly invented by someone in marketing, of how large an image the camera can take (or rather, how much resolution the image has). The following table might help you compare megapixels to scanning and printing.