This paper is based on a master thesis which is focused on statistically valid tests in the context of photorealistic visualisations (PRVs) and their perception in judgement processes such as architectural competitions. Based on documented occurrences in dealing with PRVs in this field, we have to mention specific effects like mistrust in information of PRVs in public participations, usage of certified visualisations, lack of authenticity in PRVs or even the ban on PRVs from competitions by the municipality. Further analysis in this research field discusses the state of the art and the visual communication in landscape architecture in a manifold and sometimes in a contradictory way. These findings lead to the assumption that there is a dilemma among specific features of PRVs, their usage and the viewer's perception and expectation. According to the author's knowledge this study represents the first work with this research focus. The aim of this empirical and experimental study is to research on contentual deviation (CDe) in PRVs in landscape architecture designs, their detection and reactions from viewers. Therefore it deals with influences and impacts of factors like atmospheric effects, different levels of CDes, their identification, the viewer’s focus of attention and his/her professional experience. The subsequent set-up of the practical experiment is based on the hypothesis that the viewer does not recognise any CDes in PRVs. That means that visualisations can have different information than inherent parts of the communicated design without anyone noticing it. Photorealistic visualisations of four submissions of the competition “Schinkel-Wettbewerb 2014” (Architekten- und Ingenieur-Verein zu Berlin e. V.) are manipulated according to previously developed categories and prepared for an experiment. During the research work 57 students (Bachelor and Master level) of landscape architecture rate the manipulated proposals in a role-play as juries of the competition. They evaluate the plans and write their judgment on prepared surveys while their behaviour and reaction are observed and recorded separately. The essential object of investigation stays unknown to them until the end of the experiment. The study participants recognise 5 out of 105 CDes in the whole experiment. Renderings with high-level CDes and little intense atmospheric effects are more often identified. The students of higher semesters do not see more deviations than students in the beginning of their studies. There is also no difference if the probands concentrate more on the idea of the design or on visualisations. Finally the statistical analysis of all compiled data implies that following parts of the hypothesis are acceptable: CDes are not recognised regardless of the viewer's focus and professional experience. Slight CDes and CDes in PRVs with strong atmospheric effects are not likely to be noticed. If deviations and manipulations are unlikely to be seen by students as it is shown by this experiment, can we conclude also that members of a professional jury miss a high number of them in architectural competitions? The answer is probably yes according to this study's results, which implies the level of professional experience (semester levels) did not have an influence. This raises questions in the context of competitions and their judgment structure.