Understanding Printer Resolution

A closeup of a print. Notice the individual ink dots.
Image: Wikipedia.org

When shopping for a printer, you have probably seen references to a printer’s resolution, or DPI, as a major selling point.  Many buyers have the understanding that higher is perceived as better, but few may understand what the resolution actually means when it comes to print quality.

The resolution of a printed page has to do with the number of dots, and how close they are placed to each other, referred to as DPI or “Dots Per Inch”. It is a way of measuring how much ink or toner is used to create an image, so for every inch of the image, that’s how many dots of ink or toner will be applied to the page. An inkjet model sprays dots of ink onto the page, while a laser printer drops toner onto the page as particles which are then melted and fused. Xerox printers use Phaser solid ink in a similar manner, and the results are similar.

Images and text created by a printer are made up of thousands of tiny dots being applied by the inkjet nozzles or laser printer toner in a sort of “grid” format.  Combining these thousands of dots can create any number of shapes and curves.

So why is the resolution, or DPI, so important? The more dots in a single inch, the more accurate the image will be. Curves will appear smoother, and text can appear sharper. Imagine drawing a circle by filling in blocks on graph paper. The more dense the blocks, the smoother the circle will appear. A printer with 1200 dots per inch has more to work with than one with 600 dots per inch. If you magnify a printed page, it would look similar to the image below.

For a printer with a resolution of 1200 DPI, there are 1200 dots of ink or toner for every inch of an image.  Compared to a printer that is limited to 600 DPI, one would expect the shapes, text, and images have smoother curves and sharper detail. The main downside of a higher resolution model, however, is that it takes more time to apply the extra dots, and can result in slower printing speeds.

The type of printing method can also affect the appearance. For example, inkjet models tend to produce weaker text but better photos compared to laser models, while lasers excel at sharp text. The type of paper used can also affect the quality. Inkjet ink tends to bleed into plain paper more than photo paper, for example, so choosing paper designed for your output type can get the best results for the printer’s resolution.

It is important to note that many printers are capable of printing at multiple resolutions. This provides the best of both worlds. For every day printing, for example, users who prefer faster speeds and don’t mind sacrificing a bit of quality can choose a lower resolution such as 300 DPI, while prints that need to meet the highest quality standards can be printed at a higher resolution such as 1200 DPI, taking a bit of a hit in speed. Most printers tie the resolution to one of multiple “quality” settings, though these settings can also control the amount of ink or toner used for each dot, which can result in a lighter image as well as one that is less sharp. For more information on printer quality modes, see this post.

Some printers have an “optimized” resolution that is much higher. An optimized resolution involves layering the dots by making multiple passes. This can make an image “appear” sharper or more detailed, but an optimized resolution of 2400 dpi, for example, will not actually be as sharp or detailed as a printer capable of a 2400 dpi resolution. As you might expect, these multiple passes also take more time, and use more ink and toner, which can increase costs.

When shopping for a printer, it is true that a higher DPI is generally better. Since printers with higher resolutions often cost more, however, buyers may opt for a lower DPI to save costs, or if faster speeds are a necessity. Whichever DPI you choose, you can now make a more informed decision with a better understanding of how DPI works, and what effect it will have on printed pages.