Image forming apparatus having a plurality of modes different in background potential difference

An image forming apparatus comprising:

• an image bearing member configured to convey an electrostatic latent image borne thereon at a predetermined moving speed;
• a charging member configured to charge a surface of the image bearing member;
• a charging voltage applying portion configured to apply an alternating-current voltage having a predetermined charging frequency to the charging member;
• a developer bearing member configured to convey a developer borne thereon;
• a developing voltage applying portion configured to apply an alternating-current voltage having a predetermined developing frequency to the developer bearing member;
• and
• an exposing portion configured to perform image exposure in which a first region of the surface of the image bearing member charged by the charging member is exposed at a first exposure amount for forming an image portion potential and perform background exposure in which a second region of the surface of the image bearing member is exposed at a second exposure amount for forming a non-image portion potential, the second exposure amount being lower than the first exposure amount, wherein
• a plurality of image forming modes are settable for the image forming apparatus,
• the plurality of image forming modes are different in either one of the charging frequency and the developing frequency, and
• the plurality of image forming modes include image forming modes different in a background potential difference which is a potential difference between a surface potential of the image bearing member after the surface of the image bearing member is charged and before the charged surface is exposed by the exposing portion and a surface potential of a portion of the surface of the image bearing member which has been subjected to the background exposure.