An imager has first and second photosensitive sites and an interpolator located in a semiconductor substrate. The first photosensitive site is configured to receive light having a spectral component, and the second photosensitive site is configured to measure the level of the spectral component in light received by the second photosensitive site. The interpolator is configured to estimate the level of the spectral component in the light received by the first photosensitive site based on the measurement by the second photosensitive site.