Digital Prints

Dots, Drops, & Spots
If all this talk of dots, drops, and spots is making your head hurt, it’s time to sort all this out. I asked
inkjet expert Dr. Ray Work, an internationally recognized authority on the subject, to help me clarify
the differences from an inkjet printing point of view.
Dots: A dot is the mark on the paper or other inkjet receptive material resulting from the printing of
one or more drops of ink. It is the smallest component of an inkjet-printed image.
Drops: A drop (or droplet) is that small amount of ink that’s ejected from the orifice in the inkjet printhead
that lands on the paper and forms a mark or dot.
Spots: With printing, a spot is the same as a dot.
When inkjet printers translate pixels into printed dots, it’s not a 1:1 conversion. Each pixel typically
requires lots of dots depending on its color and value.
In addition, inkjet printers can place multiple drops per dot. Some HP printers can generate up to 32
ink drops for every dot yielding over 1.2 million colors per dot.
And there’s more. Inkjet printers can eject drops from their printheads one at a time and place them at
different positions on the paper or on the same position. They can eject one or more drops on the same
position to form one dot. They can eject drops of different sizes, which results in different size dots.
They can eject bursts of drops that combine in flight prior to landing on the paper to form a single dot.
All of these amazing options are in play with the inkjet printers on the market today. (Learn more about
inkjet printers in the “Comparing Digital Printing Technologies” section.)
Dots produced by Epson 3.5
picoliter drops, some overlapping
to give secondary colors.
Courtesy of Epson America, Inc.
Apparent Resolution
Continuous-tone printers such as digital photo printers and dye sublimation devices
(explained in the “Comparing Digital Printing Technologies” section) are unique in that
their spatial and addressable resolutions are the same. That is, each image pixel ends up
being a “device pixel” at the printer end. There is no halftoning, dithering, or screening
involved; the full pixel information in terms of color and tone/value is output directly to
paper. Contone printers are playing a different game on the digital ball field.
Chapter 2 ■ Understanding Digital Printing 47