Printer Terminology for the Rest of Us

It's almost axiomatic that thriving industries create their own jargon-and nowhere is this truer than in the world of computers, where vendors borrow, adapt, and coin words seemingly on a daily basis. At some point, however, all the borrowing and punning creates confusion-especially for the people who want to use a technology.

Computer printer vendors have borrowed much of their unique dialect of acronyms, nicknames, and terms from traditional printing, but often put a different spin on the terminology. Apart from their marketing purpose, many of the predominant terms on a printer's specification page are useful clues that can help you choose the best device for your needs-if you can understand them. Here's a quick rundown of terms and concepts you need to know.

Resolution or DPI

Printers work by depositing tiny amounts of a color (ink, toner, dye) on a surface like paper; each of these units of color is called a dot-and the first thing that years of ads and marketing have taught us to look for on a printer's spec page is its DPI or dots-per-inch. This number tells us how many dots the printer is capable of fitting in a given space and, since the dots are the building blocks of text and pictures, a higher number is considered better.

You may wonder why printers have a much higher DPI than computer screens, where print commands originate: a typical inkjet these days easily exceeds 1,000 DPI, while the iPhone 4's Retina display-probably the most pixel-dense screen available to consumers-barely makes it to 300 pixels per inch (PPI generally refers to monitor resolution, while DPI analogously relates to print resolution). The reason is that most printers can reproduce a very small number of colors-for example, a typical inkjet with four ink cartridges can produce a maximum of 16 colors for each dot (known as color depth), while a single pixel on the screen is usually capable of displaying several million different hues.

In Video: How to Choose the Right Printer

On paper, therefore, special techniques such as half-toning or dithering are used to print adjacent dots in a specific pattern; because they are so tiny, once the brain perceives them, they are mixed into the intended color, thus giving the printer a wider-ranging gamut than it is possible with just its four basic ink hues.

A matter of color

When you compare printers, you must consider not only their ability to print dots in close proximity, but also how many individual colors they can print in any given dot location. Lasers and the less-expensive inkjets have only four ink reservoirs; at a given DPI, therefore, their color depth will be lower than the more expensive inkjet models that sport five, six, or even seven different ink colors. Dye-sublimation printers offer the best quality for a given DPI because it can mix inks on the paper and thus provide a virtually limitless number of colors.

Keep in mind that the final print quality depends on a lot more than the DPI rating. Inkjets, for example, literally shoot liquid ink at your page; depending on the paper, the ink could be absorbed and bleed, causing blurry edges. A laser printer, by contrast, will usually have better edge contrast because it deposits toner on the page and then melts it into place.

Finally, a quick look at your local computer retailer or online store will reveal that many printers have not one, but two resolution ratings-for example, 2400 x 1200 DPI. The first number indicates the horizontal resolution, while the second gives you its vertical counterpart. This difference is usually due to the printing head configuration and the underlying paper transport mechanics, which are designed to provide the right compromise of speed and quality to remain within the printer's final price range. In practical terms, your printer's driver will adjust the final output quality and you will not see a big difference.

Speed

Print speed is normally expressed as pages per minute (PPM). While this seems straightforward, unfortunately, there's no universal definition of what a "page" really is.

Most printer manufacturers tell you that their speed tests are based on a letter-size page with an ink coverage of five percent. The problem is that where that ink is located can dramatically affect the speed of some types of printers, while the complexity of the image and text printed could slow down some others.

For example, inkjet printers have a printing head that moves horizontally-thus, if the dots that make up the image printed are spread all over the page, the print head will have to move around a lot more than if the dots were concentrated in a single location, resulting in a lower speed. Laser printers, on the other hand, need to compose a physical representation of an entire page before they can print it; if the commands required to compose a page are particularly complex, it will take more time to output.

Different printing modes also result in different PPM ratings. Manufacturers typically provide values for color and grayscale, especially in "multi-pass" laser printers, where the paper must take a longer path to print pages of the former type. The true variances, however, are often much subtler than that. You can bet that printing in photo quality will be slower than printing in draft mode-and that the PPM branded on the printer's box is unlikely to express the speed of the former.

Therefore, it's best to take the published PPM as an indication of the average speed of a printer-the higher, the better.

Durability

Another rating that you're likely to find in the context of printer performance is the duty cycle. This number expresses the number of pages of output per month that a printer was designed to handle-typically, the manufacturer will start with this number as a goal and make a number of design decisions to satisfy it. These include the number and capacity of the paper trays, the efficiency of the printer's cooling system, the quality and resilience of its electromechanical components, and so on.

Depending on its intended usage, therefore, a printer's duty cycle can vary considerably. Less expensive consumer inkjets could have a cycle of 3,000 pages per month, while professional lasers can exceed 100,000 pages per month. When picking a printer, this number is only relevant in giving you a clue as to what kind of work it was designed to handle. Keep the duty cycle in mind as you evaluate other characteristics like ink cost and frequency of replacement, the price of maintenance kits, and so on.

Next page: What to know about memory, and the languages printers speak