An image forming apparatus, comprising: a rotatable image bearing member, which is configured to have an electrostatic image formed upon; a rotatable developer bearing member for supplying a developer to the image bearing member and developing the electrostatic image; and processing portion for processing image information so as to add a specific dot pattern to an image to be formed, wherein the image forming apparatus is configured to execute: a first image formation mode in which an image is formed based on the image information by setting a peripheral velocity ratio Vd/Vdr between a peripheral velocity Vd of the developer bearing member and a peripheral velocity Vdr of the image bearing member to a first peripheral velocity ratio ΔV1; and a second image formation mode in which an image is formed based on the image information by setting the peripheral velocity ratio Vd/Vdr to a second peripheral velocity ratio ΔV2, which is higher than the first peripheral velocity ratio ΔV1, in the first image formation mode, the image forming apparatus is configured to form an image with a first development contrast C1 and is configured to form the specific dot pattern with a second development contrast C2, which is lower than the first development contrast C1, in the second image formation mode, the image forming apparatus is configured to form an image with a third development contrast C3 and is configured to form the specific dot pattern with a fourth development contrast C4, which is lower than the third development contrast C3, and when ΔC1 (= C2/C1) denotes a ratio between the second development contrast C2 and the first development contrast C1, and ΔC2 (= C4/C3) denotes a ratio between the fourth development contrast C4 and the third development contrast C3, ΔC2 < ΔC1 is satisfied. a rotatable image bearing member, which is configured to have an electrostatic image formed upon; a rotatable developer bearing member for supplying a developer to the image bearing member and developing the electrostatic image; and processing portion for processing image information so as to add a specific dot pattern to an image to be formed, wherein the image forming apparatus is configured to execute: a first image formation mode in which an image is formed based on the image information by setting a peripheral velocity ratio Vd/Vdr between a peripheral velocity Vd of the developer bearing member and a peripheral velocity Vdr of the image bearing member to a first peripheral velocity ratio ΔV1; and a second image formation mode in which an image is formed based on the image information by setting the peripheral velocity ratio Vd/Vdr to a second peripheral velocity ratio ΔV2, which is higher than the first peripheral velocity ratio ΔV1, in the first image formation mode, the image forming apparatus is configured to form an image with a first development contrast C1 and is configured to form the specific dot pattern with a second development contrast C2, which is lower than the first development contrast C1, in the second image formation mode, the image forming apparatus is configured to form an image with a third development contrast C3 and is configured to form the specific dot pattern with a fourth development contrast C4, which is lower than the third development contrast C3, and when ΔC1 (= C2/C1) denotes a ratio between the second development contrast C2 and the first development contrast C1, and ΔC2 (= C4/C3) denotes a ratio between the fourth development contrast C4 and the third development contrast C3, ΔC2 < ΔC1 is satisfied. a first image formation mode in which an image is formed based on the image information by setting a peripheral velocity ratio Vd/Vdr between a peripheral velocity Vd of the developer bearing member and a peripheral velocity Vdr of the image bearing member to a first peripheral velocity ratio ΔV1; and a second image formation mode in which an image is formed based on the image information by setting the peripheral velocity ratio Vd/Vdr to a second peripheral velocity ratio ΔV2, which is higher than the first peripheral velocity ratio ΔV1, in the first image formation mode, the image forming apparatus is configured to form an image with a first development contrast C1 and is configured to form the specific dot pattern with a second development contrast C2, which is lower than the first development contrast C1, in the second image formation mode, the image forming apparatus is configured to form an image with a third development contrast C3 and is configured to form the specific dot pattern with a fourth development contrast C4, which is lower than the third development contrast C3, and when ΔC1 (= C2/C1) denotes a ratio between the second development contrast C2 and the first development contrast C1, and ΔC2 (= C4/C3) denotes a ratio between the fourth development contrast C4 and the third development contrast C3, ΔC2 < ΔC1 is satisfied.