In diurnal dipteran insects the potassium channels are typically of the slowly inactivating type. This channel type regulates the cell impedance according to the depolarisation caused by light stimulation. In insects active in dim environments, the potassium channels found have been predominantly rapidly inactivating. The function of this type of channels is currently under debate. In vertebrate photoreceptors several potassium channel types, including channels sensitive to intracellular calcium and pH, are expressed in the inner segments and modulate photoresponses.
Channel noise is then insignificant by comparison.