An image forming apparatus includes a developing device, an image bearing member, an image density detecting portion, a toner content detecting portion, a humidity sensor, a supplying portion, and a controller configured to control the supplying portion so that a toner content is between an upper limit and a lower limit thereof. The controller can execute setting control in which the target value of the toner content is set on the basis of an image density of a reference toner image. The controller sets the lower limit until execution of subsequent setting control, wherein the lower limit is higher when a humidity is a first humidity and an average image ratio is a first ratio than when the humidity is a second humidity higher than the first humidity and the average image ratio is a second ratio larger than the first ratio.

An image forming apparatus includes: an image former that forms an image, which is desired by a user and different from a predetermined pattern, on a sheet; an output information detector that detects output information on a first image formed on a first sheet by the image former; and a hardware processor that: acquires an correction amount of a third image, which is formed on a third sheet after the first sheet and a second sheet, according to a detection result of the first image by the output information detector and image information on a second image formed on the second sheet after the first sheet by the image former; and controls the image former so as to correct the third image based on the correction amount acquired by the hardware processor.

An image forming system includes: a density detecting section that detects the density of a toner image formed on an image bearing member by an image forming section, the density being detected as an output image density; a hardware processor which performs; tone correction in accordance with input-output characteristics data indicating the relationship between an input image density and an output image density, the input image density being the image density of a tone component included in the input image data, the output image density being detected by the density detecting section in accordance with the tone component; determining whether there is a missing tone component in the input image data; and complementing the input-output characteristics data corresponding to a missing tone component, when it is determined that there is the missing tone component.

A video count value is acquired per unit area predetermined in a direction in which a recording medium is conveyed, based on recording target image data. When an image has been formed on an area of the recording medium from which the video count value has been acquired, control is performed by using the acquired video count value so that a developing unit is replenished with an amount of toner corresponding to the video count value acquired from the area.

A developing device includes: an image bearing member; a plurality of developing rollers each supplying toner to the image bearing member, and developing an electrostatic latent image on the image bearing member into a toner image; and a hardware processor analyzing values representing density fluctuations during the toner being supplied from the developing rollers to the image bearing member, for the respective developing rollers, and correcting a control value for an image density of at least one developing roller among the developing rollers based on an result of the analyzing so as to eliminate the density fluctuations, in consideration of an effect caused at the developing roller on a downstream side in a rotational direction of the image bearing member by correcting the control value for the image density of the developing roller on an upstream side.

A controller controls a charging unit to charge a photosensitive member so that a surface potential of the photosensitive member is controlled to a first potential, controls an exposure unit to expose the photosensitive member so that a potential of an exposure region on the photosensitive member is controlled to a second potential, controls a surface potential of a developing sleeve of a developing unit to a third potential; and forms a test image on a sheet by controlling the photosensitive member, the charging unit, the exposure unit, and the developing unit. An absolute value of the first potential is larger than an absolute value of the second potential. An absolute value of the third potential is larger than the absolute value of the first potential.

The image forming apparatus includes an image adjustment unit that performs image adjustment on an image for adjustment formed on a rotary member by an image forming unit, based on the detection result by a detection unit, the image adjustment unit calculates the position of second data corresponding to the detection result by detecting an area in which the image for adjustment is formed, and calculates first data corresponding to the position of the second data corresponding to the detection result by detecting an area in which the image for adjustment is not formed, and performs the image adjustment by using the first data and the second data.

In an image forming apparatus, a storage portion stores a target adhesion amount of toner to adhere to an image bearing member at each of gradation levels as a target gradation level and a setting value of a control parameter used for control on the image forming portion at the target gradation level. A first control processor makes an adhesion amount sensor measure an actual adhesion amount corresponding to the setting value and thereafter compares a resultant measured value and the target adhesion amount and corrects the setting value if needed in association with at least one of the target gradation levels as a subject. A second control processor makes the image forming portion output a calibration image used for correcting the target adhesion amount using a period when the first control processor performs processing if there arises a need to correct the target adhesion amount associated with the subject.

An integrated sensor has a density detection sensor, a sensor board, and a potential sensor pattern. The density detection sensor detects the density of a toner image formed on a toner image carrying member. On the sensor board, the density detection sensor is mounted. The potential sensor pattern is provided on the sensor board, and detects the potential of the toner image.

An image forming apparatus for forming a toner image on a sheet includes a main assembly, an image forming station provided in the main assembly and configured to form a toner image on the sheet, and a fixing portion provided in the main assembly and configured to fix the toner image formed on the sheet, on the sheet, the fixing portion including a fixing rotatable member and a covering member covering the rotatable member. The image forming apparatus also includes a suction mechanism including a duct connected with an opening provided in the covering member, and a fan configured to suck air inside the covering member through the duct. The air sucked by the suction mechanism is discharged into a space in the main assembly other than a space through which the sheet passes.