I printed the test image in three modes – Standard, No Graphics, and Toner Save – because of a queer artifact in the prints. Take a look at the scans:
The black smudge in the most problematic area of the image strikes one’s eyes immediately. Could the drum have got dirty? I printed in other modes, but the defect persisted. So there is obviously an error in the driver’s processing of the print task.
The discernable details in the image correspond to a resolution of 600dpi. In the Toner Save mode only the bottom and left borders of objects are printed, while solid fills are replaced with a sparse regular dot pattern. The resolution suffers from that, of course.
The halftone image looks good enough at the standard settings. The lightest and darkest tones are printed sharply: you can distinctly see the borders between the areas of the gray-scale. By the way, halftones are printed using a mixed method: the dot size as well as the distance between the dots of the pattern is varied.
The graphics are greatly distorted in the Toner Save mode. The fill density is lower; the darkest tones are inverted; there are no distinct borders between mid-range grays. This mode doesn’t suit for printing graphics at all and it hardly saves too much of the toner. You should use this mode only when you are not printing halftones.