"A model to explain subjective evaluations of the apparent size of an object seen through a diffusive media"

M JAEN; CORREGIDOR DIEGO; ELISA COLOMBO

Toulouse

Congreso; 34th European Conference on Visual Perseption; 2011

The perception of objects through diffusive media like an atmosphere with fog or smoke, or an eye with cataracts is clearly affected; visual cues are strongly modified in such a way that can induce, for example, to a car driver to make serious and "expensive" mistakes. Overestimation of distances and underestimate of speeds in diffusive media have been assessed subjectively but there are no complete models which allow these perceptual effects to be described in detail. In the present research we have carried out two experiments of subjective determination of the apparent size of clearer and darker objects than its background, placed at different distances of a diffusive media (a polycarbonate diffusive filter used for special effects in cinema and TV was useful for this purpose). Three observers with normal vision have carried out the subjective evaluations under the different experimental conditions. A theoretical model was developed that predicts how apparent size of an object diminishes as a function of distance to diffusive media, depending on the diffuser´ modulation transfer function (MTF) parameters. The agreement reached by the model in the experiments´ conditions is acceptable within the experimental uncertainties but it also allows predicting extreme conditions that have not been experimentally tested.