The Evolution of Photo Printing

Much has evolved in photography printing over the last twenty years. Less than ten years ago, developing negatives at professional photo labs seemed the natural thing to do. Today, developing A3-sized, lab-quality photos at home, in minutes, at a fraction of the cost is the norm.

Behind the beautiful prints that today’s consumer photo printers are capable of, lie the history, development and features of different photo printing technologies in these modern photo printers. Learning a little about these will help you better appreciate the incredible engineering behind them, and make you a more discerning buyer.

Modern photo printers fall into three major categories: dye sublimation printers, thermal inkjet printers and Micro PiezoTM printers by Epson. Here is a brief explanation of how they work and what you should know about each:

Dye Sublimation Photo Printing Technology

Dye sublimation printers are very simple and are highly similar to developing photos the traditional way using film. Unlike the other two ink-based technologies explained later, dye sublimation printers work by printing with a ribbon that has sections of cyan, magenta, yellow and black dye instead. Each colour is transferred onto the paper or film using a print head that heats each colour on the ribbon, causing the colour dyes to vaporise, and deposits them onto the surface of the paper where they return to solid form. This is process is repeated for each colour on the ribbon as the paper moves past the print head four times; and the separate colours combine to form all the gamut of colour hues and tones required.

This technology has become popular with the recent proliferation of compact photo printer models that use it. But due to the very slow speed and high price of the print ribbons involved with dye sublimation printing, printers that employ this technology are limited to producing small-sized photos like the common 4x6-inch type, and it is totally impractical and costly for high volume photo printing, or for secondary purposes like printing documents.

The two other mainstream home photo printing technologies work by shooting liquid ink onto the printing medium. However, the way they do it is dramatically different.

Thermal Inkjet Technology

Although thermal inkjet technology was invented in the late 70s, it was only in the late 90s that it started becoming popular for home photo printing. The technology works by electrifying microscopic resistors in tiny ink chambers behind the print head’s nozzles to rapidly create an intense heat that, for a nanosecond, is close to a million degrees centigrade – hotter than the surface of the sun! This violent and sudden increase in temperature vaporises ink to create a bubble that expands so rapidly, some of the ink literally explodes out of the nozzle onto the paper. When the bubble cools and contracts, the resulting vacuum pulls more ink into the print head from the cartridge.

Due to the high degree of wear and tear caused by the extreme heat involved in the printing process, thermal inkjet printer heads tend to have much shorter life-spans compared to those of other photo printing technologies. Hence, many thermal inkjet cartridges come with integrated print heads so that a regular replacement is ensured when the ink depletes and the cartridge, with the print head, is changed. However, the integration of a print head makes thermal inkjet cartridges typically more expensive.

Epson Micro PiezoTM Print Head Technology

In the engineering world, some materials have what is known as a “piezoelectric” property, meaning that they physically bend or change shape when an electric current is passed through them. Since the 1970s, Epson has researched this phenomenon for use in photo printing as an alternative to thermal inkjet technology, culminating in the launch of their first Micro PiezoTM photo printer in 1994 – the world’s first high resolution (720dpi) colour inkjet.  Today, Epson has further refined its proprietary Micro PiezoTM print head technology and remains the only maker of consumer photo printers that employs this advanced technology.

In a Micro PiezoTM printer, elements made of piezoelectric materials are constructed into the ink chambers behind the nozzles in a print head. To shoot the ink through the nozzles, an electric current is passed through the piezoelectric elements, causing them to bend and thereby mechanically force the ink out through the nozzles onto the printing medium.

The volume of ink being shot out of the nozzle can be precisely controlled by varying the electrical charge given to the piezoelectric elements in the ink chambers. This enables ink droplets as small as 1.5 picolitres – or 1.5 times a trillionth of a litre!

This ability to produce such minute droplets allows Micro PiezoTM technology to produce sharper, higher resolution and grain-free photo prints compared to the other technologies. In addition, Micro PiezoTM printer heads run much cooler than thermal inkjet print heads and thus, can last much longer. This results in more affordable ink cartridges that, unlike many thermal inkjet cartridges, do not need integrated print heads.

The lower heat involved in Micro PiezoTM printing also allows printers that employ the technology to use a wider range of inks like UV-curable and solvent-based inks for printing on special uncoated vinyl media like stickers. These inks are too volatile for use in the high heat operation of conventional thermal inkjet printers.

Indeed, we have come a long way in the quest to perfect photo printing at home - from the low cost thermal printing of the 80s to the high precision Micro PiezoTM print heads of today.

Consumers are presented with the power of affordable home printing that exceeds the print quality of even photo labs through technologies like Micro Piezo printer’s variable ink droplet sizes that enable super high print resolutions, and an amazingly wide colour gamut of millions of colours with the use of multiple colour inks; on top of their ever-increasing print speeds.

The Future of Photo Printing

Indeed, much has evolved over twenty years. Now, if a time traveller from twenty years in the future appears and tells us that by then, we would be able to print A1-sized 3-D images or textured replicas of famous art pieces within a second from our Micro PiezoTM home printers, would you believe him? Considering the progress we have achieved in home photo printing in the last two decades, we should not be surprised at this notion.