cell phone images (IMAGE) Johannes Gutenberg Universitaet Mainz Caption Cell phone cameras adjust the brightness of a scene using a single value, which explains why the sky is overexposed in the top image and the ground is underexposed in the lower image. The eyes of flies and humans, on the other hand, can generate stable responses to contrast even when there are changes to background luminance. Credit photo/©: Marion Silies Usage Restrictions Credit must be given to the creator. Only noncommercial uses of the work are permitted. No derivatives or adaptations of the work are permitted. License CC BY-NC-ND Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.