Inkjet printers produce images by spraying lots of tiny dots of ink onto the paper through lots of really tiny nozzles (my printer has 6,144 nozzles, for example). If you look at an inkjet print through a magnifier, you’ll see that the image consists of tiny ink dots. Today’s photo inkjets use truly tiny ink droplets (from five picoliters to as small as one picoliter—a picoliter is one-trillionth of a liter!), and can place one million to 23 million of them per square inch of print (using as many as 32 droplets to produce a single colored dot), so you won’t see the dots at normal print-viewing distances.

The photo inkjet printers from major manufacturers such as Canon, Epson and Hewlett-Packard (HP) all turn out excellent prints. Here are some things you should consider when choosing a photo inkjet.

RESOLUTION
Just as “megapixel” is the magic marketing term for digital cameras, “dpi” (dots per inch) is the sacred spec for inkjet printer marketing staff. Today’s photo inkjets have resolutions ranging from 1,440 x 720 dpi to 9,600 x 2,400 dpi. But as is the case with camera megapixels, a printer’s dpi figure isn’t the ultimate arbiter of image quality. More important are droplet size and the highly guarded proprietary algorithms that control how the droplets are put on the paper. The quality of the ink and paper used (and their compatibility) also have a bearing on image quality.

For practical purposes, 1,440 or maybe 2,880 dpi is plenty for inkjet prints. Beyond that, you probably won’t be able to see much difference in a print and will just use up more time and ink per print.

Keep in mind that image resolution (megapixels) and printer resolution (dpi) are two different things. Camera resolution tells you how many pixels make up the image. Printer resolution tells you how the printer puts the ink on the paper. A 6-megapixel image will contain 3,000 pixels across by 2,000 pixels down, regardless of how small or large you view it. A 1,440 dpi printer will print at 1,440 dpi regardless of the image resolution. To make an optimum inkjet print, you should have an image resolution of 200 to 300 pixels per inch of print size.

INK TYPES
Inkjet printers use two types of inks: dye-based and pigment-based. Historically, dye-based inks have produced brighter colors but had a shorter print life, while pigment-based inks have produced longer print life but less bright colors. Today, both types produce excellent images and very good print life.

Commercial four-color printing uses four inks to produce full-color images in magazines like this one: cyan, magenta, yellow and black. Early inkjet printers worked with inks of these four colors. Today, photo inkjet printer manufacturers use additional inks to produce smoother tonal gradations, better neutral tones and truer colors—up to 10 inks, depending on the model. The first photo inkjets to exceed four inks added light cyan and light magenta inks, which resulted in prints with more color nuances and smoother skin tones. Then came multiple black inks for richer black tones, smoother grayscale gradations, better colors and improved black-and-white prints.

INK TANKS
My first inkjet printer had two ink tanks: one containing the black ink and one containing all three color inks. The advantage of this system is that you only have two tanks to deal with. The disadvantage is that if you print, say, a lot of scenic shots with sky areas that use up the cyan ink first, you have to toss a lot of good yellow and magenta ink when you replace the out-of-cyan tank. Today, most photo printers utilize separate tanks for each color. Thus, you need replace only the color that has been depleted, especially economical when your printer uses five or more colored inks.

The printer is actually the least expensive part of desktop printing; ink and paper costs can quickly exceed what you paid for your printer. Printer manufacturers’ inks are always consistent and match the printing profiles. Third-party inks can be an alternative; they’re less expensive, but you’ll probably have to do a lot of testing to make them work their best. Also, keep in mind that using third-party inks can void your printer’s warranty.

Some photographers use a second printer set specifically for black-and-white printing and equip it with special grayscale inks, which are available only from third-party suppliers. This way, they don’t mess with their color printer at all and get the best of both worlds. On the other hand, the new photo inkjets that use multiple black inks turn out great monochrome prints without the need for a second printer.

PAPERS
Inks are only part of the equation. A wide variety of media is available for photo-quality prints. See our companion article on printing papers for a full account (“Choosing Photo Paper,” page 60).

LONGEVITY
Early inkjet prints didn’t last very long. When exposed to light (as when being displayed), they would fade in just months. Printer manufacturers solved that problem, coming up with ink/paper combinations that resist light-fading for many years. Unfortunately, light isn’t the only thing that can shorten print life. Atmospheric gases (such as smog) can rapidly destroy a relatively lightfast image, as can high temperatures, humidity and rough handling. Today, Canon, Epson and HP all offer inks and papers that provide excellent longevity, but note that some ink/paper combinations produce better longevity than others; if long print life is important (sometimes it’s not), check the manufacturers’ specs for the combos you’re considering. For an objective look at print permanence, visit www.wilhelm-research.com.

SPEED
The printing speeds listed in the specifications for printers are often for draft mode, printing text and graphics, not photos. Check the specs for times for printing true photos. Also keep in mind that the spec speeds are the time the paper spends being printed, not the time from the moment you click the “print” button until the finished print comes out. The size of the image file, and the speed of your computer and printer connection (FireWire, USB 2.0 or 1.1, etc.) also figure into the total time. Several companies offer direct-printing 4x6-inch printers that eliminate the computer and external connection.

FORMAT
Photo inkjet printers come in several sizes or formats. You can choose from a variety of excellent printers that make prints up to letter size (8.5x11 inches) for well under $200, and you can get printers that will turn out dandy 13x19-inch prints for around $500. The larger-format printers also allow you to make smaller prints (I make mostly letter-sized prints with my 13x19-incher), so if you want to make big prints even once in a while, you probably should get a large-format printer. If you have no need for prints beyond letter size, get one of the letter-format printers.

Many photographers prefer borderless prints, but not all photo inkjet printers can produce them. If you like borderless and don’t like trimming prints, be sure to choose a printer that can make borderless prints.

By the way, just as the megapixel count is just one of the factors that accounts for digital camera image quality, dpi is just one of the factors that accounts for print quality. Ink quality, the paper used (and its compatibility with the ink), printer driver settings, the size of the ink droplets and how they’re placed on the paper and combined to produce the various colors—all of these factors and more are part of the equation.