An image sensor includes a plurality of pixels for converting incident photons into electrical charge; an overflow drain to draw off excess charge from at one or more of the pixels; a mechanism for summing charge from two or more of the pixels; a first network of resistive devices generating a first overflow drain voltage where at least one of the resistive devices has, in parallel, a fuse that can be opened in response to an external stimulus to provide the optimum overflow drain voltage for pixel anti-blooming protection and saturation signal level for when a plurality of pixels are summed together; and a second network of resistive devices connected to the first network of resistive devices generating a second overflow drain voltage where the second overflow drain voltage is a fraction of the first overflow drain voltage and the second overflow drain voltage provides the optimum overflow drain voltage for pixel anti-blooming and saturation signal level for when none or substantially none of the plurality of pixels are summed together.