How to make thin lines visible

snowingsky · Joined: 30 Mar 2010 Posts: 8

How to make thin lines visible?
Problem Description:

Thin lines (hairlines) are almost not visible when printing in a higher resolution.Thin lines do print more visible on a black and white printer than on a color printer.

Solution

When we say that a laser printer can print 1200 dots per inch will this mean that it can lay down 1200 monochromatic dots per linear inch. The apparent color produced by a color laser printer is accomplished by placing several dots of four colors in near proximity at differing angles in order to trick the eye into believing that there is a particular color (which is approximately how color televisions accomplish the same task using three colors). This means that the smallest useful unit to consider for this discussion would be the smallest group of pixels capable of producing a color that we will call a color cell.

When a fine line is struck across the page, only the pixels it actual touches can be considered for activation and of these only the ones that participate in generating the color of the line will actually be "turned on" (with respect to the screen being used). If you print the same document on a monochromatic printer (like the 3260) the thin lines will strike a higher number of pixels which will all be "turned on" since black is the only 'color' that makes sense.

Example:
On a monochrome printer each square would represent a single dot at 300 dpi, 4 squares would make a dot at 600 dpi, and 16 squares would make a dot at 1200 dpi. Now draw a thin line across the page. At three hundred dpi any square that the line
touches would get turned on, at 600 dpi the quarter part of each square would get turned on, and at 1200 dpi a pixel only gets turned on if the line touches a sixteenth part. Any part of the line that does not exactly touch a pixel "falls off the page" (still,since every dot can form the only color available, this can render fairly thin lines).

300 dpi 600 dpi 1200 dpi
If the resolution gets higher, the dots are getting smaller. If the color of the line is not 100% black, the intensity of the line will also change due to the For color printers the problem gets even worse. After deciding if the line actually
touches a pixel we have to decide whether or not the pixel it touches is a component of the color being printed with respect to he halftone being used (this definition varies with modifications to the color space caused by color management options -- which is
why so settings worked slightly better). Because of the angles of the screen this will cause even fewer consecutive pixels to be turned on (resulting in the fine, dotted, or missing lines). Since the smallest practical unit to consider on a color printer is the
smallest group of dots that can represent a given color, then the thinnest unbroken line drawable of a given color will be that which passes through these color cells on a contiguous path (the exact size here depends on the color, halftone and particular engine).

The only workaround in this case would be to change the drawing to some
monochrome (Cyan, Magenta, Yellow or Black), which would only provide a marginal
improvement. Also, if actual lines where used rather than a bitmap there would be an
additional improvement (likely more than making the bitmap monochromatic).