The associated simultaneous corner growth is referred to as midtone jump. The geometry of the joining corners, combined with the high film thickness of screen-printing inks, contribute to how much midtone jump we experience. Round dots maintain their circular geometry throughout the tonal range. In midtone areas, all adjacent dots connect at tangents as shown in Figure 1. And because the angles are so tight, it is very easy to fill in the area between dots with ink.
Printers select round dots for two reasons.
The second reason relates to the printing process used. Consequently, the round dot automatically tends toward an ellipse. And as we'll soon discuss, this helps to minimize midtone jump. But in screen printing, a round dot remains round and provides no benefits to the printer. This reduces the potential for tonal jumps due to filling in and makes these dot shapes the best choice for screen printing.