A solar energy collection system has a solar receiver with an external surface configured for high absorption of light incident thereon. The solar receiver also has a plurality of light-reflecting elements arranged on the external surface. The light-reflecting elements produce at least partially diffuse reflection of light energy incident thereon. Heliostats concentrate solar radiation onto the external surface of the solar receiver. An imaging device provides a digital image of at least a portion of the external surface of the solar receiver. A controller can control the heliostats in response to apparent brightness of the light-reflecting elements as represented in the digital image.