An image forming apparatus stores a plurality of patterns, each pattern defines at least an irradiation energy amount and irradiation position(s), which facilitate the irradiation of a photosensitive member in accordance with image data. Irradiation of a photosensitive member effects the formation of latent images along the surface of the photosensitive member. The latent images are developed using a toner carrying member which includes a thin film developing sleeve which confronts the photosensitive member and carries toner.