Printer Primer 1: Choosing a Photo Printer
Whether you came of age in the days of darkroom chemicals or began photography in the digital era, there are few things more satisfying than seeing your image on paper as a finished print. Current technology has made producing exhibition-quality prints from the comfort of your own home easier than ever before.
The first step towards achieving high quality prints involves choosing the materials and equipment best suited to your needs and, of course, budget. In the first of this two-part primer we'll explore some basic printer technology so you can make informed decisions as you wade through the numerous options on the market.
In the pursuit of photo-realistic prints that rival or exceed what you'll get from online services or the local drugstore, there are two broad printer technologies from which to choose; dye-sublimation (dye-sub) and inkjet. Dye-sub printers rely on a heating process to mix dyes onto a specially coated paper, producing a continuous tone print. An additional clear protective layer is added over the dyes, making them less prone to scuffs and smears when the print is handled.
|Print output of consumer level dye-sub printers is typically limited to 4 x 6 inch postcard sizes or smaller.|
Dye-sublimation technology is used only in a relatively small number of consumer-level compact photo printers such as the Canon Selphy lineup (pictured above) and Polaroid's POGO series printers. The specialized media required for these printers is brand-specific, and normally packaged as an integrated paper/ink set which is loaded into the printer.
The overwhelming majority of dedicated photo printers on the market today are inkjets. These printers spray discrete, but tiny droplets of ink onto specially coated papers via a printhead that makes multiple passes across the print surface.
Although these ink dots do not mix together before being ejected onto the print surface, they are extremely small; so small that they're measured in picoliters (trillionths of a liter). Complex dot placement algorithms known as dithering, along with paper coatings designed to maintain image sharpness and vibrancy, are capable of producing literally millions of colors with tonal gradations that appear smooth to the naked eye. Inkjet printers come in a variety of forms.
|Compact inkjet photo printers can be operated without a computer connection. Images (typically 4 x6in) can be printed directly from a USB-connected camera, a memory card or even a Bluetooth enabled mobile device.|
|Desktop models often include input trays for printing directly onto CDs/DVDs|
|Many 13- inch and wider printers include an attachment that allows you to print on rolls, for image lengths extending beyond the standard sheet sizes.|
Ink on paper
At the heart of inkjet printer technology are the printheads, which actually eject the ink as they move left to right across the width of the print surface. Printheads contain rows of tiny openings, called nozzles. As the printhead makes a full pass across the print surface, a motor in the printer advances the paper line by line, exposing un-inked areas to a set of ink-firing nozzles.
|In a piezoelectric printhead (left), an electrical charge triggers a mechanical element which then pushes a drop of ink through the nozzle. In a thermal inkjet printhead (right), a thermal element heats the ink very rapidly, creating air bubbles whose pressure forces ink droplets out of the nozzle.|
Piezoelectric printheads can eject variably-sized droplets from a single nozzle position, allowing for crisp, finely resolved image detail. Thermal printheads typically offer a high density of nozzles per printhead, which increases print speeds. Though there are differences as regards production cost and usable lifespan, both piezoelectric and thermal printheads are capable of producing very high-quality photographic prints.
Making dots invisible
With inkjet printers, the illusion of smooth, photo-realistic tonal gradations is achieved by using extremely small ink droplets and adjusting their size and spacing to produce darker or lighter areas of an image. Simply put, a series of dots packed tightly together on the page will create a darker tone than dots of identical density that are spaced further apart. The problem, of course, is that if there is too much space between dots, our eyes will pick them out as individual shapes. Indeed, in the early days of the technology, a telltale sign that a photograph had been printed using an inkjet printer was the appearance of visible dots in the highlight tones of an image, where wide spacing of ink dots on the paper was needed to achieve light densities of tone.
|While inkjet prints give the appearance of smooth output to the naked eye...||...a 13x magnification shows a dither pattern of small dots spaced close together. Images courtesy custom-digital.com.|
This explains why in today's prosumer-level photo printers you often see not just the traditional colors of cyan, magenta, yellow and black (CMYK) but diluted versions, such as light cyan (LC), light magenta (LM) as well as light black (otherwise known as gray). These secondary inks work in conjunction with the CMYK primaries to make seamless transitions from darker to lighter tones. Because their density value is lighter, these secondary inks can be spaced close enough to hide individual dots from the naked eye, yet still yield the print densities necessary to create subtle highlight detail.
|These days, inkjet printers designed for high quality photographic output use separate cartridges for each ink color. Individual colors run out at different rates, meaning you will be replacing colors one at a time, rather than all at once. In printing, 'K' means black. In this Epson printer, PK designates 'photo black', LK 'light black' and LLK 'light light (ie lighter) black'.|
Printer companies offer a range of models, differentiated by price. Moving up from an entry-level inkjet photo printer to one of the 'professional' models can bring a number of advantages. The most obvious is the ability to produce larger prints. Instead of being limited to 8.5 inch-wide/A4 paper, larger desktop models can accept 13 inch- up to 17 inch-wide sheets. The common inkjet paper sizes beyond letter-size include 11 x 17/A3, 13 x 19/Super A3, and 17 x 22/A2 sheets.
Another benefit of the larger pro-level desktop models is that they are designed to handle thicker, heavier fine art papers that can be difficult or impossible to load reliably into letter-size printers. Purchase price aside, larger printers can actually be less expensive per-print than letter-size/A4 models making them less expensive to operate over the long-term. This is because they use larger capacity ink cartridges.
Even if you rarely need to make a large print, if you plan to print on a regular basis, you may quickly make up the cost difference of buying a larger printer in ink savings alone.
Black and White Printing
Due to inherent ink impurities, one of the more difficult things to do is to achieve neutral monochrome results by mixing color inks. Therefore, printers most appropriate for black and white output will employ one or more additional black inks.
|A printer with multiple dilutions of black ink has many advantages when producing black and white output. As with secondary cyan and magenta inks, the light black/gray inks can produce detail much more faithfully in the highlight regions. These dilutions also reduce or in some cases eliminate the use of color inks, achieving more neutral output and reducing the degree of color shift, (technically referred to as metameric failure), that can occur as you view the same print under different light sources.|
Dyes and pigments
One important distinction you'll find on printer spec sheets is the type of ink being used. Dye inks are used in a vast majority of the photo inkjet printers on the market. They can produce highly saturated colors and are relatively inexpensive to produce. Dye inks, however, have poor lightfastness characteristics, so they are susceptible to noticeable fading over relatively brief periods of display. For photographers whose primary concerns are image stability and longevity, printer companies offer models that use pigment inks.
Pigments are more fade resistant in a greater variety of display environments than dyes. While the range of hues and saturation (known as color gamut) pigments can produce has grown significantly in the last few years, they generally exhibit a smaller color gamut than their dye-based counterparts. If image permanence is a concern, keep in mind that inks are only part of the story. The paper on which you print those inks is equally important, as are the environmental conditions in which the print is displayed.
Black ink types
Pigment-based inkjet printers ship with two separate full-density black inks. One is formulated for glossy papers (usually labeled Photo Black) while the other (Matte Black) is designated for use with matte papers. Some printers will have to purge ink lines each time a matte black/photo black switch is needed, wasting precious ink. Should your printer behave in this manner, the best way to minimize waste is to dedicate printing sessions to either matte or glossy paper instead of switching back and forth after each image.
Standard paper choices
Printer companies offer a range of house-branded papers on which to print, featuring a variety of brightness levels and surface textures. The broadest distinction, however, is between matte and glossy papers. Glossy papers exist in a range from smooth highly reflective papers to more subtle finishes with a hint of texture. The descriptive designations 'luster', 'semi-gloss', 'satin', 'photo', and 'film', to name a few, all refer to glossy papers. As a rule, glossy papers have a wide color gamut, offering the greatest range of hues and saturation. They yield very rich prints with a high degree of contrast.
Matte papers, by comparison have a relatively muted gamut and produce weaker blacks. Their attraction lies, in large part, to the wide variety of surface textures available. Papers with a prominent 'tooth' can lend a fine-art air to appropriate subject matter, more closely resembling a traditional ink on paper work rather than a typical photograph. The choice here of course is one of personal preference. As we will discuss in a coming article, however, the printer companies' papers are only a starting point, as there exists a robust, exhibition quality paper market from third party vendors.