As grayscale print head technology evolves and becomes a viable solution for true production-level superwide/grand format inkjet printers, it’s important to address the impact variable drop grayscale printing has on how the industry measures print quality.
The spatial measure of resolution in dots per inch (dpi) is only relevant when measuring single/binary droplets. In this paper, we will discuss how apparent resolution, or the way an eye perceives an image as having greater detail than it does in physical reality, should be used as the new standard for judging final print quality.
Light colors are used as a means to trick the user’s eye into perceiving the print as having a higher resolution than the native resolution. In other words, light colors offer a second, lighter level of detail to an image to reduce the grainy appearance of skin tones and quartertones, in particular. Light colors are typically 40% of the optical density of the dark colors. So, if you are printing a light blue of 40% density, for example, the printer will use nearly 100% of light cyan instead of the usual 40% coverage of dark cyan. Although more ink is used, the light color gives the print a nice, smooth fill, resulting in an apparent increase in resolution of 1.5. So, an image printed at 600 x 360 dpi, an average resolution of 464 dpi, appears closer to 700 dpi with the use of light inks. Similarly, a 1000 x 720 dpi print with light inks has an apparent resolution of 1200 dpi.
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