An image forming apparatus includes an image bearing member, a voltage applying portion, a feeding portion, a detecting portion, a storing portion, a controller for controlling a first operation in which on the basis of a detection result of the detecting portion, a kind of the recording material set in the feeding portion is stored in the storing portion, and a second operation in which an adjusting chart is outputted for adjusting a transfer voltage; and an inputting portion. In response to a single start instruction, the controller is capable of carrying out control so as to execute the first operation and the second operation for outputting the adjusting chart prepared by transferring a plurality of test images onto the recording material from which an index interrelating with the kind of the recording material is detected by the detecting portion in the first operation.

A controller generates first supplement density data from certain parts of a plurality of density input values and a plurality of pieces of first detection density data by at least one of interpolation and extrapolation of a plurality of pieces of first detection density data, generates second supplement density data from other parts of a plurality of density input values and a plurality of pieces of second detection density data by at least one of interpolation and extrapolation of a plurality of pieces of second detection density data, and generates gradation correction data using the plurality of pieces of first detection density data, the plurality of pieces of second detection density data, the first supplement density data, and the second supplement density data.

An image forming system includes an image forming section that prints an image on a recording medium and outputs the recording medium, a color measurement section that measures color of the image printed by the image forming section, an imaging unit that captures the image printed by the image forming section, and an analyzer that analyzes, based on the image captured by the imaging unit, whether or not the image subjected to color measurement by the color measurement section has an abnormality. When the analyzer determines that the image has an abnormality, the color measurement section does not output a color measurement result of the image having the abnormality.

An image forming apparatus includes an image bearing member, a voltage applying portion, a feeding portion, a detecting portion, a storing portion, a controller for controlling a first operation in which on the basis of a detection result of the detecting portion, a kind of the recording material set in the feeding portion is stored in the storing portion, and a second operation in which an adjusting chart is outputted for adjusting a transfer voltage; and an inputting portion. In response to a single start instruction, the controller is capable of carrying out control so as to execute the first operation and the second operation for outputting the adjusting chart prepared by transferring a plurality of test images onto the recording material from which an index interrelating with the kind of the recording material is detected by the detecting portion in the first operation.