Patent ID: 8224208

Claim:
An image forming apparatus comprising: an image bearing member; a plurality of development units configured to form an image on the image bearing member; a development rotary configured to serially switch each of the plurality of development units to an image forming position at which an image is formed on the image bearing member; an intermediate transfer member on which the image formed on the image bearing member is transferred; and a control unit configured to give an instruction to start forming of the image if a mark that is a reference of starting the forming of the image and is provided on the intermediate transfer member, is detected, wherein the control unit is configured to compare a first time period, which is a time from start of switching of the development unit to detection of the mark, with a second time period, which is a time taken for switching the development unit, and if the second time period is shorter than the first time period, configured to start switching to a subsequent development unit by moving the subsequent development unit to the image forming position after the image is completely formed by the development unit existing at the image forming position.