Printers: Bubble jet technology
If you want colour prints up to A4 (210 x 297mm), or even A3+ (329 x 483mm), you need an ink jet printer. As the name suggests, ink is sprayed onto the print media – very precisely – and the tiny drops of coloured ink are used to build up the picture. Canon’s bubble jet (BJ) printing technology is a development of the ink jet-printing concept. Canon has recorded over 10,000 patents for bubble jet technology, which it introduced in 1983. Prints from some of the latest BJ machines are virtually indistinguishable from prints made on conventional photographic paper.
How it works
A bubble jet printer works using heat. In very simple terms, an ultra-fine nozzle is connected to a reservoir of ink. At the front of the nozzle is a very small heating element.
When the element is switched on, a bubble forms inside the nozzle and a tiny drop of ink is expelled at high speed. When the drop hits a paper surface, it forms a round dot of even density and colour. The heating element is switched on and off in response to data from a computer, which processes the information from an image file. The computer may be a desktop unit, or a microprocessor inside your EOS camera, or inside the printer itself. The process takes place at incredibly high speeds. Some printers eject up to 22,000 drops of ink per second.
If an image were printed one dot at a time, it would take several days before the print was ready. To speed things up, Canon uses multiple nozzles for each colour of ink and combines all the nozzles into a single print head. This print head passes back and forth across the width of the paper in the printer. Each nozzle is separately controlled from the computer so that the right amount of ink, of the correct colour, is deposited in the right position on the paper. As soon as one narrow band of colour has been applied, the paper moves forward for the next band to be applied. The Pixma 950i (now discontinued) ejects ink through 3,072 nozzles, enabling it to print an A4 photo in about a minute.
The early inkjet and bubble jet printers were handicapped by the size of the dots they could drop onto the paper. The bigger the dots, the more ‘grainy’ the final image looks and the coarser the transition between tones. The new Pixma printers output tiny droplets of ink, each smaller than the diameter of a human hair and containing a miniscule 2 picolitres of ink. (A picolitre is 0.000000000001 litres). The smaller the droplet, the more droplets it takes to make up any given area of a print, and the finer the detail that can be reproduced. These tiny droplets of ink, combined with high precision ink and paper placement, mean that Pixma printers produce prints with exceptionally smooth tonal transitions.
According to Canon, Bubble Jet technology produces ink dots of a more consistent size than the inkjet piezoelectric crystals used by some other manufacturers. Ink bubbles created by heating are very consistent and are only ejected onto the paper when they reach a certain size. With some conventional inkjet systems, ink can be ripped away from the print head, producing varying ink dot sizes.