There are several key specifications which consumers can use to differentiate between inkjet printers.
The speed at which the printer prints to a page will be listed under the term pages per minute, or ppm. These figures can be problematic for consumers, however, as printer vendors frequently cite ratings based on printing only the simplest text documents or printing at a low resolution, such as in draft mode. Speeds listed on the box, therefore, can be up to three times faster than the reality.
Top level inkjets will boast of up to 20ppm in monochrome (draft quality), and 12ppm in colour, but if you're looking at a mid-range product, expect to see figures from 8ppm to 16ppm in monochrome, and 1.2ppm to 12ppm in colour (draft to best quality printing modes).
Resolution and print quality
The quality of the print from a printer is indicated by its resolution. Resolution refers to the number of dots in a square inch (dots per inch or dpi) that a printer can spit out onto a sheet of paper.
Inkjets generally have a maximum colour resolution of 2400x1200dpi, with some high-end models boasting of up to 4800x1200dpi. But even if you plan to print a full-colour 8x10in photograph, you're unlikely to see any significant improvement once you get above 1200x1200dpi. In addition, many printers employ 'optimised dpi', which involves the use of software and proprietary technologies to interpolate an image and to smooth out patches of colour, fill in gaps, and sharpen more detailed sections. Such enhancements can affect print quality as much as the printer's resolution.
Just as important as a printer's resolution is the size of the ink droplets it deposits on the paper. Just about every photo printer (more on these below) on the market is capable of producing droplets sizes measuring four picolitres or less (one picolitre is the equivalent of one billionth of a litre). Much smaller than this and the droplets will be imperceptible to the human eye.
As a result, the best way to determine print quality is not to look at the resolution specs alone, but to print a sample and judge for yourself.
Interface and operating system capability
Virtually all inkjet printers now available connect to your PC system using a USB interface, with some offering both USB and parallel connections.
There are many USB 2.0-ready printers available in the market, but don't be dismayed if you find your system doesn't support the newer USB standard. Although speed is certainly an issue when printing digital photos, in practice, the major bottleneck to the speed of the printer will be the actual print mechanism rather than the connection method.
Also, few printers come with the relevant USB or parallel cable, so check that you have such a cable or you'll need to buy one.
Likewise, make sure your PC meets the operating system requirements before choosing a printer model. Some entry-level printers may still feature printer drivers which support Windows 95, but you're most likely to need Windows 98 or higher, as well as a CD-ROM or Internet access to install the printer software.
Unlike with laser printers, inkjet users won't be able to upgrade the built-in RAM capabilities of their printers.
This shouldn't be too much of a concern for consumers, though. According to Epson, inkjets are a type of raster device, which means they only need enough memory to be able to process a line of data at a time. These types of devices rely on technology which requires the PC to render pages before sending them to the printer. In other words, the processing of the data happens on the PC, not the printer, as is the case with laser printers. This means that there is no need for large amounts of RAM to be included in the printer itself, and upgrading memory is redundant.
RAM capacities nevertheless vary slightly across printer models. Entry-level desktop printers can come with as little as 768KB of RAM, while photo printers generally feature more built-in RAM: most come with at least 8MB of internal RAM. This is to accommodate the extra burden of printing high-quality, dense images.
Some inkjet printers targeted at the SOHO market will be slightly larger than those designed for residential users, to accommodate different paper sizes. These inkjet models could be worth looking out for if you do require larger or more specialised paper handling capacities such as A3, B5, A5, A2, index cards or transparencies.