Step 1: Create true continuous tone images with ultra-high resolution
For high-end colour printing applications, there is a traditional divide between contone and halftone output.
Contone prints on photographic paper are widely regarded as the benchmark for image quality, longevity, colour fidelity and competitive cost; whilst halftone methods have become something of the default for text, line art and convenience.
Halftoning was developed in the nineteenth century as a way to reproduce black and white photographs in newspapers. It reduces shades to patterns of dots of different sizes, shapes or spacing which could be printed with a single ink. Halftones simulate continuous tone images by optical illusion: the human eye blends the dots into single tones.
Colour halftone printing with multiple screens is more complicated, as it is important to keep the different coloured dots close together to fool the eye into seeing different colours. However, grouping the dots into rosettes is essential to avoid unwanted visual effects like moire patterns, and this ultimately forces compromise.
Continuous tone photographic images on silver halide are different. They contain an infinite range of colours within a very large gamut, and no dot structure. They are produced via a wet chemical process that uses the reaction of light on substances in the photo-sensitive paper to achieve incredibly smooth images. This is wonderful for pictorial graphics and photographs, but historically has had a softness that makes it less successful for text and fine detail.
LumeJet uses continuous tone and therefore can offer natural and faithful reproduction of colour tones. However, we achieve that with none of the historical compromises that have limited sharpness for text and graphics.
While others claim 400 dpi resolution (as good as the eye can see), in reality they are achieving only 400 dpi 'addressability' given cross-talk and interaction between pixels. If pixel size is actually bigger than 63µm or interacts heavily with its neighbours, then it is impossible to achieve a genuine 400 dpi resolution even if the centres of the pixels are 63µm apart. The impact is a softening or blurring of the image, and colour bleed in fine details and reversed text. You cannot make a jigsaw look right if the pieces don’t actually fit together.
LumeJet’s technology permits the creation of a pixel of the correct size, with all colours perfectly aligned, in a manner that practically eliminates interaction with any neighbouring pixel. We describe it as “true 400 dpi continuous tone”.
The result is the sharpest photo print on silver halide, ever, which also enables the reproduction of fine text and graphics:
...but true, high resolution, continuous tone is not the whole story of how LumeJet achieves its quality...