Visual experiments, attesting visual preference, visual ranking and visual differentiation, are very important to academia
and industry. They are traditionally performed into laboratories under controlled viewing conditions, resulting very
costly in their execution, due to the time and effort involved by all participants. If controlled tests could be substituted
by uncontrolled tests, a potential serious improvement could be obtained by eliminating a large part of the cost. In this
work we investigate if, and to what extent, visual experiments performed under controlled viewing conditions can be substituted by uncontrolled experiments. A task of visual preference of prints is carried out. This task is performed in the laboratory, under controlled viewing conditions, and in many different places, under natural, artificial and mixed light. We observe statistical equivalence for preferences expressed in controlled or uncontrolled conditions that supports the hypothesis that visual preference can be assessed with uncontrolled tests.