- — 21 July, 2005 15:21
- What is a photo printer?
- Injekt printers and dye-sublimation
- Image quality
- Cartridges and paper
- Photo printer terminology
Inkjet printers and dye-sublimation
Photo printers fall into two main categories: inkjet printers and dye-sublimation printers (also referred to as thermal dye or dye-sub printers). The former are inexpensive, partly because the same technology is widely used in other printers. The latter can cost slightly more (both for purchase and supplies) but give superior results.
As their name implies, inkjets work by squirting tiny jets of ink onto the paper through nozzles. The size of the droplets is measured in picolitres. This plays a role in determining overall quality, but there's no need to get too hung up on droplet sizes, as other factors such as the paper you use are arguably more important.
Basic inkjets use four ink colours: cyan, magenta, yellow and black, which are combined to produce the required output. Many photo printers use additional cartridges to better reproduce difficult subjects such as skin tones -- light cyan and light magenta, or red and green are typical add-ons. More specialised models may have additional black and grey inks, which is useful if you favour black and white photography, but not necessarily useful otherwise. As well as these colour elements, additional gloss layers may also be added to create the finished appearance of a shiny photo or to provide protection against UV or water damage. Inkjets can print on ordinary paper, but produce much better results on media specifically designed for photos.
One advantage of inkjets is that they also produce very acceptable text output for general printing use and are often used in multifunction devices that combine printing, scanning and faxing. Conversely, dye-sublimation printers are less useful for general printing, but can produce better images with fewer visible dots. They must be used with special dye-sub paper.
Dye-sublimation systems effectively fuse material from an ink ribbon onto the page, using a variety of thermal techniques. This allows them to handle continuous tone images (such as skin tones or skies) more effectively than some inkjets, although the differences are no longer very marked. A waterproofing layer is also usually added as part of the printing process.
One advantage of dye-sublimation printers is that their ink consumption is more predictable, since they essentially use a fixed amount of ribbon per printout. This is reflected in the popularity of printing packs which combine ink and media for a specific number of photos. Such packs are also common for inkjets, but usage on those tends to be more variable, especially if they're also used for non-photo tasks.
While printer manufacturers like to quote resolution figures in dpi (dots per inch), these are deceptive when it comes to print quality. Most modern photo inkjets offer a resolution of 1200 by 4800dpi, which is more than adequate for almost all photo-printing tasks. On dye-sublimation printers, the quoted resolution is often lower (around 300 by 300dpi), but because of the different printing technology, the overall quality is equally good.
In practice, the resolution of the original photo will also have a major impact (though any additional resolution above 300 pixels per inch is unlikely to benefit the average home photographer). Adjustments made by image editing software, the amount of extra data stored by the camera (discussed below) and the quality of ink and media will also have a major impact.
A related question is that of speed. Some photo printers claim speeds of up to 12 pages per minute (ppm) for non-photo tasks but, in reality, printing any kind of photo will be a much slower process. If you can get a 6x4in standard-sized photo to print in a minute, you'll be doing pretty well on most systems. Some printers offer an optional countdown to tell you how long the printing will take, though these estimates aren't always trustworthy.
Cartridges and paper
If you're printing photos at home regularly, you'll quickly run up big bills for both ink cartridges and photo printing paper. While generic office paper is fine for happy snaps on the fridge, the results with "proper" photo paper are notably better. As a rule of thumb, using the printer manufacturers' own ink and paper will also give better results than mixing and matching.
With that said, original manufacturer ink is often considerably more expensive than third-party replacements (printer manufacturers make most of their profits from supplies), so you may want to experiment with cheaper versions. Ink prices tend to range from $30 to $70 or more for a cartridge, while photo paper costs around $1 for an A4 sheet, with discounts for buying in bulk.
Manufacturers like to outdo each other with guarantees of how long their ink and paper will last, with some claiming images produced using their technology will last as long as 100 years. Remember though, one advantage of digital formats is that it's much easier to produce new prints when needed, so don't get too obsessed with archival numbers.
Incidentally, ink cartridge lives are often quoted as a cartridge duty cycle number, but this will tend to be an overestimate for many photo-printing tasks due to their high ink usage. As noted above, dye-sublimation printers tend to have more predictable ink usage.
Photo Printer Terminology?
Printer specifications often contain a bewildering selection of abbreviations and technical terms. Here are the important ones to know about:
DPS and PictBridge: Printing directly from cameras has always been a key goal for the digital imaging. Direct Print Standard (DPS) was developed by six major camera and printer companies -- Canon, HP, Epson, Fujifilm, Olympus and Sony -- to define how images could be sent directly from cameras to printers in a standard fashion. The standard debuted in December 2002.
The practical implementation of DPS is known as PictBridge, which was developed by the Camera & Imaging Products Association (CIPA). PictBridge utilises USB to connect the camera to the printer and a format known as Picture Transfer Protocol (PTP), developed by the International Imaging Industry Association, to transfer the images. While PictBridge simplifies the process, manufacturers often tweak their own devices to work better with each other (eg, in practice, directly printing from a Canon camera to a Canon printer will be easier and more flexible than printing from a Canon camera to an HP printer). The DPS standard also incorporates DPOF (see below). PictBridge support is a useful feature of your printer if your camera supports it.
DPOF (Digital Print Order Format): allows camera users to specify on their camera which images they wish to print and in what quantities. This can be useful if you expect to mostly manipulate your images in-camera and print them directly (either to your own photo printer or to a DPOF-supporting kiosk in a retailer). If you plan to upload your images to a PC for manipulation or archiving before printing, then DPOF is less useful.
EXIF (EXchangeable Image File): This is the format in which pictures are stored on most cameras, combining a JPG image with additional information about the picture. Printers use EXIF data, which can include PIM information (see below), to help enhance their output.
PIM (Print Image Matching): Technology developed by Epson and licensed to many other manufacturers which stores information about individual images to help in better printing them. PIM was designed to expand on the mid-1990s Design Rule for Camera File (DCF) standard, which was widely agreed on by camera manufacturers but didn't offer a wide enough range of colours for modern inkjet printers. PIM data is incorporated into EXIF files, and includes contrast, sharpness, brightness, saturation, as well as a number of other parameters.
ICM (Image Colour Matching) and ICC (International Colour Consortium): Two standards for matching what you see on screen with what you see elsewhere. ICM is built into Windows, while ICC is a much more comprehensive beast which provides colour profiles for different devices (including cameras, monitors and printers). Effective ICC support is more a matter of software than hardware. In practice, such colour matching technologies are mostly used by professionals.