Printers are still concerned with craftsmanship and are always looking for means to produce faster print jobs with improved quality. The invention of new halftone screening techniques is one of the methods imaging companies have used as an attempt to improve the quality of the printed piece. These techniques can possibly improve the aesthetic qualities and fidelity of printed reproductions, therefore printers and students of printing need to study these techniques to ensure that the benefits outweigh the costs of implementation.
This experimental study was conducted to measure the quality of printed halftones that were screened with three different dot structures; conventional, alternative (XM) at 240 lpi, and alternative (XM) at 340 lpi. The printing of the halftones and tone scales was completed using accepted printing practices.
The analysis was focused on two questions; is there a difference in the tone scales created with the use of the alternative screening when measured with print industry equipment, and is there an improvement of the apparent quality of the halftones when evaluated by members of the print community and laypersons?
With the use of a densitometer and a spectrophotometer, the tint patches and tone scales were measured to determine a difference in color, density, print contrast, and dot area. Through statistical analysis, it was determined that a significant difference was created with the use of different screenings.
The Delta E values were also calculated with the collected CIELab measures. Delta E is the measure of the color difference between two colors. If the value calculated is above two and a half or three, then the difference should be perceptible by the human eye. Overwhelmingly, the Delta E values show no humanly perceptible difference.
When evaluating the apparent quality of the halftones, many people reported that they saw no difference; the average number was thirty-two percent for printers and forty-four percent for non-printers. The participants who did perceive higher quality in one versus the other were fairly equally spread across the three screening methods and quality factors.
Therefore, the only conclusion that can be drawn from this research is there is a measurable difference in the screening methods but the difference is humanly imperceptible and is not commercially significant for commercial offset lithography.