Scanners: Features explained
Today's scanners are versatile; many scan slides and negatives as well as paper, and almost all come with software for editing images. Plus most come with an optical character recognition program (OCR) for converting hard-copy text into editable documents.
Resolution
Resolution is particularly important for scanning slides
The amount of detail picked up by a scanner is determined by its resolution, which is measured in dots per inch (dpi). Generally speaking, the higher the dpi, the clearer the image.
A resolution of 1,200dpi is fine for most tasks, but enlargements require a higher resolution to maintain image quality. For scanning film, select an optical resolution of about 2,400dpi.
Quality
All the scanners on test exceed these requirements. However, a higher resolution doesn't necessarily mean higher quality scans: one model on test with a maximum resolution of 3,200dpi is just as capable of producing great scans as one with a top resolution of 6,400dpi.
File size
Scanning at such high resolutions produces massive files (around 60 to 70MB apiece - a typical digital photo is around 1MB, by comparison).
The scanners' default resolution settings are much lower (around 200 to 300dpi). It's best to experiment with a number of test scans at these settings before cranking up the resolution.
Speed
Those planning to scan regularly should factor speed into the buying decision. But remember, scan speeds will be affected by your computer's USB connection. You'll get best results with the high-speed USB 2.0.
Additional features
Image-editing software
Scanners come bundled with useful software. Some can automatically remove scratches and specks of dust; in advanced mode you can do image adjustments such as tweaking the colour balance.
Generally all scanners also come with third-party image editing software to enhance your scans.
Optical character recognition (OCR)
This software converts scans of words into text documents that can then be edited in a word processor. This is handy for digitising old type-written items.
One-touch scanning
Some scanners let you scan directly to a PDF of email at the touch of a button.