Abstract: We propose to enhance the capabilities of the human visual system by performing optical image processing directly on an observed scene. Unlike previous work which additively superimposes imagery on a scene, or completely replaces scene imagery with a manipulated version, we perform all manipulation through the use of a light modulation display to spatially filter incoming light. We demonstrate a number of perceptually motivated algorithms including contrast enhancement and reduction, object highlighting for preattentive emphasis, colour saturation, de-saturation and de-metamerization, as well as visual enhancement for the colour blind. A camera observing the scene guides the algorithms for on-the-fly processing, enabling dynamic application scenarios such as monocular scopes, eyeglasses and windshields.