In this digital age most photos are created as electronic jpg files inside our cameras, but sometimes we need to scan old photos, drawings or paintings as digital images for projects. Currently we are designing the cover and interior or a biographical book. Many of the old photos we plan to use in the book were taken decades before the invention of the digital camera. I would like to share some basic information about scanners so you know what to consider when buying a desktop scanner. Some of our clients prefer to scan the old photos and give us the files.
Scanners are popular tools for doing desktop publishing and web design. You’ll find a wide range of scanners available—from a low-cost black and white hand-held variety to high-quality, professional color devices. For the highest quality, printers and service bureaus use expensive drum scanners. The high-quality scans they produce are required for high-end printing projects such as book and magazine covers, images for coffee table books, and advertisements. A skilled operator using a CCD (charge-coupled device) flatbed scanner can produce similar high-quality scans.
Optical Resolution
When determining which scanner to use for your work, look for optical resolution specifications. These are two numbers that indicate how many pixels per inch (e.g., 600 x 600 PPI) are scanned in each direction. (I suggest you ignore the interpolated resolution numbers—these are measurements made when the scanner inserts new pixels between scanned ones.)
How much resolution your scan needs depends on how you plan to use your scanned images. For example, photos for offset printing are usually scanned at 300 PPI. Line art (such as black and white pen and ink illustrations) for offset printing need to be scanned at 1200 PPI to ensure that the lines are smooth. Images to be printed on desktop laser or color inkjet printers are scanned at 100 to 200 PPI. Photos and line art for the Internet are scanned at 72 PPI while images for PC-PowerPoint presentations are 96 PPI. Text that will be converted to text characters (using OCR technology) are scanned at 300 to 400 PPI.
Eye-Popping Tip. Always scan your images at the final size you plan to use them. Do not enlarge your scans, as they will lose resolution.
Dynamic Range
Most flatbed scanners have a dynamic range of about 2.4. If you need to display better detail in shadow areas or you plan to scan negatives and slides, you may be better off using a top-quality color flatbed or drum scanner that can provide a dynamic range of 2.8 to 3.2.
Bit Depth
Most color scanners are at least 24-bit, which results in near-photographic quality in terms of the range of colors. Scanners that are 30-bit and 36-bit can capture billions of colors. I recommend these for scanning slides and negatives, but beware that few software packages can open these files. Note: Not all monitors can display 24-bit color. If you’re using an 8-bit (256-color) monitor, then a 24-bit image may look blotchy on screen.
Other Considerations When Buying a Desktop Scanner
In general, CCD (charge-coupled devices) produce better scans than low profile, less expensive scanners. Make sure the scanning bed is large enough for your documents. Consider the scanner’s speed and determine if you need a slide adapter. Sheetfed scanners take up less room on your desktop, but you can’t scan a 3-D object or book using this kind of scanner.
An option that may come with a scanner and affect its cost is software. Yes, you will need to have photo-editing software (such as Adobe Photoshop) to create quality scans, especially from less-than-perfect originals.
Eye-Popping Tip: OCR (optical character recognition) software allows a scanner to read handwritten or printed text, then convert it into text characters that can be read by any word processing software. OmniPage and Text Bridge are examples of two OCR software programs.