The Stouffer 21-Step Transparent Guide serves as a gauge to evaluate the variables encountered in the exposure and processing of lithographic plates and photographic materials by contact. It indicates the direction and magnitude of exposure or processing adjustments necessary to achieve the desired results. It is also used with contact positives, silk screen, printed circuit boards, and most other photographic applications for judging results, determining speed and contrast of emulsions, and hardness of coatings.