The SUSTAINED unit in the insect lamina is characterized by spatial and temporal adaptive properties. These characteristics were observed and recorded by Arnett. Neural mechanisms explaining these characteristics have since been proposed by Ogmen. This paper presents a very simple neural model, based on shunting inhibition, that also explains the experimental results. Two versions of the model, one employing feedforward spatial adaption and the other employing feedback spatial adaption, are discussed. Both models exhibit adaptive properties that are potentially useful in optical sensor systems such as compression of signal range. This type of adaption is especially important because it reduces the amount of information that must be handled by post processing systems.