How we test.... scanners

Computer Shopper tests a scanner’s performance using typical real documents. In addition to the two timed scans that we graph with each review (plotted against an average score based on previous tests) we carry out a range of tests using various original documents and different resolutions.

We time how long a scanner takes to generate a preview of its full scan area, and how long it takes to capture an A4 document. To test higher resolutions, we make scans of a 6x4" photograph at 600 dots per inch (dpi) and at 1,200dpi. We test scanners that can capture film using a variety of positive and negative 35mm film strips, working up to each scanner’s highest optical resolution.

Finally, we use a reflective Q60 colour calibration target to help us assess a scanner’s colour accuracy and its ability to capture detail among very light and very dark shades. We examine all of our captured test images for sharpness, colour accuracy and for problems such as the speckling caused by digital noise. We compare scans against the saved output of other scanners we’ve tested.

A4 speed

WHAT IT DOES: This test shows how many A4 scans a scanner can make in a minute. We perform the test with the scanner’s lamp already warm from previous previews and scan tests. We use a higher resolution than most scanners’ 150dpi default to make the test a little more taxing. This test typically produces an image file of around 25MB, so it can highlight a slow interface too.

Film speed

SETTINGS: 2,400dpi resolution, default colour depth

WHAT IT DOES: A decent film scan requires a resolution of at least 2,400dpi, so we time our scans using this resolution. Our results are presented as the number of scans per minute the scanner is capable of.

The test is performed with the scanner’s film backlight already warmed. We disable any hardware or software noise reduction, or any other filters or processes that could slow down the results. We time from the moment the scan button is pressed, stopping the clock when the scanner’s driver returns control to the user.

Test bed

Intel Pentium M 1.6GHz notebook
1GB DDR RAM

Reference scores

A4 speed 3 scans per minute
Film speed 2 scans per minute