There are two areas to look at when testing laser printers: speed and print quality. We used a range of different documents to test the different aspects of each and weighted the results to give the Quality and Speed scores.
Speed
There were three main things to look for in terms of speed. The first was the time it took for the printer to spool up and print one page, the second was the maximum speed when printing typical office documents, such as letters or emails. The third was the speed when printing heavily formatted documents that include graphics.
To test the spool up time we used a single page document with just one full stop in the corner to minimise print processing time, and make just the physical print engine the bottleneck. This test was weighted at 10 percent of the overall Speed score.
The second speed test used the same document, but with ten pages, each with just one full stop. This test showed the absolute maximum speed of the printer, including spool up time, when printing 10 pages. This test was also weighted at 10 percent of the overall Speed score.
Our third speed test was more real world, and used a typical single page office letter, 10 copies of which were printed, and this made up 40 percent of the final Speed score. The final speed test was the Torture Test. This was a 30 page document with very heavy formatting, bitmap and vector graphics, Word art and clipart, page boarders, watermarks, embedded Excel graphs and a grab bag of different fonts and colours. While the other tests determined the speed of the print engine, this test was specifically designed to stress the print processor, and this made up 40 percent of the Speed score.
The results of the letter and torture tests are displayed below.
Quality
These days all laser printers are capable of producing excellent text results. All the printers tested delivered clear black text that was well defined and sharp at regular point sizes. Given this, it's with graphics, gradients, small text and other difficult printing tasks that the good printers were distinguished from the poor.
Our main quality test was the printer test page, and there was one for monochrome printers and another one for colour. The mono test page had text of varying font sizes, ranging from 6pt up to 18pt, both black on a white background, and black and white on a 50 percent grey background. While most text was clear on all the printers, we looked for any malformed characters at small font sizes, especially on the grey background.
Under the text was a high-resolution image with many subtle levels of tone. This was printed in monochrome to see how the printer translated the colour into grey levels. We looked for poor dithering, which can result in gradient banding, as well as over- or under-saturation of toner and, finally, horizontal print banding.
At the bottom of the page was a grey gradient that goes from 0 percent to 100 percent in 256 levels. Most printers will use dithering to represent different levels of grey, so we looked for noticeable dithering artefacts as well as whether the middle of the bar was accurately 50 percent grey.
The colour test page was the same as that used for inkjet printers, and consisted of a series of C (Cyan), M (Magenta), Y (Yellow) and K (Black) bars and blends. It also had fine lines and a block of pure black, and one of composite black, which was made up of C, M and Y but no K. We looked for dithering in the blends, colour purity and brightness, accuracy of the lines and whether the drivers were clever enough to replace the composite black with K.
