In the process of lighting design, usually many lighting alternatives are assessed against criteria such as energy consumption, lamp type, price and also user preferences collected through psychovisual experiments. However, these experiments induce subject fatigue, which limits the number of lighting alternatives that can be evaluated. To overcome this limitation, we propose a new protocol based on (1) the use of the internet and (2) an incomplete experimental design in which each subject judges only a subset of the whole set of visual stimuli. This protocol is validated by comparing three experiments conducted in the laboratory and online. No statistical difference was highlighted between the results of the experiments. Extrapolations suggest that this protocol could be used to assess up to 3000 visual stimuli.