Image forming apparatus that sets peripheral velocity ratios

An image forming apparatus comprising:

• an image bearing member;
• a developer bearing member configured to develop an electrostatic image formed on the image bearing member using a developer;
• a driving unit configured to drive to rotate the image bearing member and the developer bearing member;
• a latent image forming unit configured to form an electrostatic image on the image bearing member by forming a light-part potential and a dark-part potential in the image bearing member;
• and
• an application unit configured to apply a developing voltage to the developer bearing member,
• a control unit configured to control a developing contrast between the developing voltage and the light-part potential of the image bearing member,
• wherein the image forming apparatus is configured to transfer a developer image borne on the image bearing member to a recording material to form an image on the recording material in an image forming mode which is a first mode and a second mode which is a wider color gamut than the first mode,
• wherein an electrostatic capacitance of a portion of the image bearing member is designated as C, the portion is supplied with the developer borne on the developer bearing member,
• the developing contrast is designated as ΔV,
• a charge amount per unit area of the developer borne on the developer bearing member is designated as Q/S, and
• a peripheral velocity ratio is designated as Δv, the peripheral velocity ratio being the ratio of the peripheral velocity of the developer bearing member to the peripheral velocity of the image bearing member,
• the first mode is set so that a relation of |Q/S×Δv|≤|C×ΔV| is satisfied, and
• the second mode is set so that a relation of |Q/S×Δv|>|C×ΔV| is satisfied, and
• wherein, when a second electrostatic capacitance is larger than a first electrostatic capacitance, the control unit controls so that a second developing contrast set in the case of the second capacitance is smaller than a first developing contrast set in the case of a first electrostatic capacitance.