Effect of Lens Color on Target Visibility for Air-Sea Rescue

Abstract

Visual detection of life rafts in the sea presents a difficult task to personnel engaged in air search and rescue operations. A possible means of aiding this task is to use an appropriate sun-glass filter with light transmission properties designed to reduce glare and atmospheric attenuation, while enhancing target-to-background contrast. To examine and evaluate this possibility, target acquisition performance associated with the following types of sunglasses was compared with that of the unaided eye: (1) Haze master (yellow), (2) Oakley-Doc (pink), (3) Cosmetan (brown) and (4) N-15 (gray). The experimental approach involved the use of a circular 1:1000 scale terrain model and associated techniques simulating an air-sea rescue operation. Each subject searched for targets while making a simulated banking turn around the model. The performance of ten subjects for each experimental lens condition was measured in terms of response time and number of targets found. Results based on these measures showed the Oakley-Doc lens to be the best and the Cosmetan to be the worst of the lens alternatives. However, no filter was found to be superior to the unaided eye. The data are in agreement with a number of recent target acquisition studies which show no advantage in using yellow lenses. The results are, moreover, consistent with the assumption that supposed enhancement properties of colored lenses may well be offset by losses in light transmission associated with their use.