What is Ink Density?

Density or reflective density to be more accurate, is a measure of the percentage of reflected light. In printing his usually means the percentage of light that is reflected from the paper and the ink. It is a convenient metric to use in a print production environment, since it provides insight through a one-dimensional variable by which press operators can judge whether too much or not enough ink is being laid on the paper.

It is one variable of many used for controling color on press.