The Canon Selphy CP780 Compact Photo Printer ($99.99 direct) is the latest incarnation of a basic design that Canon's been selling for years: a highly portable small-format dedicated photo printer, built around a thermal-dye print engine. As you would expect, each new generation has improved on the last—or at least tried to. For example, the new version is a little faster than last year's CP760, and offers a different set of pluses and minuses for its photo quality. Like the CP760, it's a capable printer that's well worth considering.

Like most dedicated photo printers, the CP780 can print from a memory card, a PictBridge camera, or a computer. Unlike many, it can't print from a USB key, which means you can't easily print an image you've already moved to your computer or an optical disc without connecting to your computer. Canon also sells an optional Bluetooth adaptor ($49.99 direct) for printing from phones and other Bluetooth devices.

One small plus for the printer is that it can print photos at more than one size. Small format most often translates to printing at 4 by 6 inches only, but Canon sells print packs for photo sizes ranging from credit-card size to 4 by 8 inches. Many if not most people may never use the other sizes, but it's nice to know that you can if you want to.

Another plus is portability. Most inkjet–based dedicated photo printers and even some thermal-dye printers are about the size of a lunchbox, or bigger. The CP780, however, is just 3.0 by 6.9 by 5.2 inches (HWD) and weighs only 2.1 pounds. Add the optional battery ($79.99 direct), and you have a printer you can easily take with you, even to an outdoor event like a picnic or a Little League game, to print photos on the spot.

Setting up the CP780 is absolutely standard for a small-format thermal-dye printer: Slide the ribbon cartridge in, load paper, plug in the power cord, and you're ready to print directly from a memory card or camera. If you want to print from a computer, too, you can run the installation program from disc and connect using a USB cable.

The LCD screen for previewing photos remains unchanged from Canon's last-generation printer. It's a meager 2.5 inches, and it doesn't tilt, which means you have to move your head rather than the screen if you're having trouble seeing the image being displayed. This is well behind the curve for current printers. The similarly priced Editors' Choice Epson PictureMate Dash, in particular, offers a 3.6-inch tiltable screen. The CP780's built-in menu is somewhat limited, but it's easy to use, with options that include red-eye correction, image optimization, and color control using predefined settings, including vivid color, black and white, and sepia.

Almost all the photos on my tests qualified as true photo quality, but not top-tier quality, largely because of a slight soft-focus effect. The effect is subtle enough, however, that most casual photographers may not mind it, or even notice it. It's hard to see in most photos unless you compare them with output from other printers. For the most part, the quality is a match for what you can expect for photos from your local drugstore.

The CP780 also shows one other flaw that I've seen repeatedly in Canon small-format photo printers. When it's printing from a computer, but not when it's printing the same file from a camera or memory card, thin diagonal lines, such as the spokes in a bicycle wheel, come out with jagged edges. Given that this happens only when it's printing from a computer, the problem appears to originate in Canon's driver. And given that few images have diagonal lines in any case, it counts less as a real problem than as a potential occasional annoyance. Still, it's troublesome that Canon has never bothered to fix it.

Very much on the plus side, the photos are reasonably rugged—both water and scratch resistant. You can safely pass a stack of photos out for people to browse through without worrying that they'll come back scratched or smudged. They also should last a long time. Canon claims a 100-year lifetime for photos kept in dark storage, as in an album; 30 years for photos kept behind glass; and 10 years for photos exposed to the air.