Effects of Background Reflectance and Illumination Level on the Estimated Freshness of Vegetables

Luminance distribution information is a critical cue for estimating visual freshness of vegetables, such as strawberries 1 and cabbages 2. However, it remains unclear how robust is the freshness estimation against environmental variation, such as variations of lighting and background conditions. Therefore, we conducted an experiment to investigate the effect of several environmental parameters on our visual estimation of fresh vegetables by controlling the image information. First, we took calibrated pictures of fresh vegetables: cabbage, carrot and komatsuna (Japanese Mustard Spinach) that gradually degraded in a controlled environment. Next, to investigate the effect of the luminance contrast on freshness estimation, we created stimuli with several levels of luminance contrast between the vegetable surface and the background by controlling their luminance level. As a result, we found that the background reflectance do not affect visual freshness estimation. On the other hand, visual freshness estimation depends on the absolute luminance levels of the vegetable surface but it saturates over a certain illuminance. Those results suggest that visual freshness estimation is quite robust against environmental variation except when the illuminance level is low.

Okajima, K., Sakurai, Y., Arce-Lopera, C. A. (2013). Effects of Background Reflectance and Illumination Level on the Estimated Freshness of Vegetables (vol. 42). Perception.

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