Image forming apparatus controlling formation of test images based on recording material type

An image forming apparatus comprising:

• an image bearing member configured to bear a toner image;
• an image forming portion configured to form the toner image on the image bearing member;
• a transfer member configured to form a transfer portion where the toner image is transferred from the image bearing member onto a recording material;
• an applying portion configured to apply a voltage to the transfer member;
• and
• an executing portion configured to execute an output operation for forming and outputting a chart formed on a recording material on which a plurality of test images are transferred by applying a plurality of test voltages to the transfer member by the applying portion,
• wherein the plurality of test voltages include a first test voltage of a first voltage level and a second test voltage of a second voltage level higher than the first voltage level, and
• wherein the executing portion changes a difference between the first voltage level and the second voltage level based on a kind of the recording material on which the chart is formed.