1. An image forming apparatus, comprising: an image transferring member configured to receive and transfer a toner image; a plurality of image bearing members configured to bear respective toner images on respective surfaces thereof, the plurality of image bearing members including, a first image bearing member configured to carry and transfer a reference image pattern onto the image transferring member; and at least one other image bearing member configured to carry and transfer a corresponding image pattern onto the image transferring member; at least one detector configured to detect the reference image pattern and the corresponding image pattern; and a controller configured to control the first image bearing member and each of the at least one other image bearing member to have a positional relation for which a sum of an elapsed time differences between the reference image pattern and the corresponding image pattern is reduced.