At least one exemplary embodiment is directed to an exposure apparatus which includes an illumination optical system configured to irradiate a mask with light from a light source, and a projecting optical system configured to project a pattern image of the mask onto a substrate. The illumination optical system provides a first light intensity which can be altered by an optical unit forming a second light intensity. The second light intensity can be further altered by an optical unit changing the dimension of the second light intensity forming a third light intensity, where the third light intensity can be used in the lithographic process for forming devices.