If you have been comparing different printer models, you may have seen a reference to picoliters as a measurement of the size of droplets. In inkjet cartridges, a nozzle technology is used to dispense miniscule droplets of liquid ink on the paper that combine to make the images and text. In general, the smaller the drops are, the more accurate the final print will be. Much like pixels of a digital camera, the higher the number, the better the color quality will be. The size of the drops are closely related to printer resolution. For printing with ink, the resolution of prints is measured by DPI, or dots per inch. The size of inkjet droplets is measured in picoliters, a measurement so small it is unseen to most human beings. This microscopic dot of printer ink is typically written pL, but pl is also widely accepted.
A picoliter is a subdivision of a standard liter. It is essentially 1/trillionth of a liter, or 1 millionth of a million. If you were to think of a 1 liter bottle, and divide it into 1 million drops, then divide each of THOSE drops into 1 million drops, that is how small a picoliter is. An average raindrop would be equal to hundreds of thousands of picoliters.
As an example, the Epson Stylus NX420 has a droplet size of 3 picoliters, while the HP OfficeJet 4500 printer has a droplet size of only 1.3 picoliters. The second printer has smaller drops, and therefore can put twice as many drops into the same space occupied by one drop from the first, providing better control over colors.
The general idea for printer ink technology is that the smaller number of picoliters of ink transferred to the page in a single “dot”, the sharper the output and the more refined the colors will appear. This is generally true, but it is not the whole story. Factors like the quality of the original image, the actual DPI (dots per inch) setting and other factors can often have more of an impact on quality. There are also a few potential downsides. Smaller dots mean it often takes more dots to produce an image, which can mean slower printing speeds. Another potential issue is that print heads may be more prone to clog as they get smaller and smaller.
While understanding the concept of picoliters is useful, especially as they relate to print head technology, the truth is that most buyers should not concern themselves with this measurement when shopping for a printer. Other aspects such as speed, size, and resolution capabilities are going to be much more important for the average user.