In the midtones, dot area grows to the point where the corners of adjacent dots join. This creates huge problems for our printing process. When the corners of the joining dots connect, they immediately bleed together, creating a condition we know as dot gain. 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.