Properties and models of the Human Visual System (HVS) are the fundaments for most of efficient objective image or video quality metrics. Among HVS properties, visual masking is a sensitive issue. Many models exist in literature. Simplest models can only predict visibility threshold for very simple cue while for natural images one should consider more complex approaches such as semi-local masking. Our previous work has shown the positive impact of incorporating semi-local masking in image quality metric according to one subjective study. It is important to consolidate this work with different subjective experiments. In this paper, different visual masking models, including contrast masking and semi-local masking, are evaluated according to three subjective studies. These subjective experiments were conducted with different protocols, different types of display devices, different contents and different populations.