Although it may seem logical to look for all the answers in the ink we use, the solution, which will be addressed in next month's installment, is actually found in the ink and another basic component of our printing process, the screen. Tone skewing All printing processes produce dot gain, and many printers attempt to measure and compensate for it. We measure the mechanical gain due to a physical change in the perimeter of the dot during the transfer process. Optical gain is the result of light refracting at the perimeter of the printed dots, causing them to appear larger, as well as to measure larger, than their actual size. We sum the optical and mechanical gain value to arrive at total gain.
PITS produces dot gain and dot loss.
Although we routinely measure and compensate for mechanical and optical gain, we do not currently take PITS-related gain into account at any stage of the process. Since this type of tone-curve skewing is not compensated for in the film positive, we still suffer gray balance error in our prints. Illustration 2B demonstrates how the profile of the previously printed dots ensures that the stencil won't make contact with the substrate during later print passes. The more stacking that occurs, the greater the likelihood that subsequent dots will collapse or flow from the stack and out of their expected positions, distorting prints and leading to excessive gain. While they show themselves differently in print, these problems remain the fraternal twin products of our stencil when it is not optimized for four-color printing.