Beacon AB has been producing Gobos for some time. A Gobo is a small round sheet used in projectors almost like a slide. It is used mostly in the commercial and entertainment business. Today these Gobos are created by using a film (also called mask). A digital exposure machine called LIOS has been developed to make it possible to create Gobos using direct exposure.

An efficient market implies that the use of fundamental analysis should not result in excess return, and that any return exceeding the market average can be explained by compensation for risk, accord-ing to The Capital Asset Pricing Model (CAPM). The focus of this study is to test whether the suc-cessful investment strategy developed by Piotroski (2000) generates excess return on American data, after risk adjustment by using Fama & French?s (1993) 3-factor and Carhart?s (1997) 4-factor CAPM. Initially we form stock portfoLIOS based on companies characterized by high book-to-market values, additionally, we divide them into different performance classes by ranking them with Piotroski?s (2000) measure of financial performance, F_SCORE.