To extend the operational envelope of helicopters, the benefits obtained from the usage of different sensors (and combination of sensors) on the one platform are being extensively assessed. Critical to the success of such approaches are image interpretability and resultant pilot workload. The particular case addressed by this paper is that where two sensor inputs are available: one from the visible (image intensified) band and one from the IR band. An adaptive image fusion processing scheme is proposed in which scene metrics are used to provide feedback control data. The use of scene metrics which are derivatives of the image fusion process is proposed in order to maximize system performance.