An image forming apparatus includes a first sensor configured to measure measurement images on a first photoreceptor, a second sensor configured to measure measurement images on an intermediate transfer member, and a controller. The controller controls a first image forming unit to form first measurement images, wherein the first measurement images are formed along a rotation direction of the first photoreceptor, and controls the first sensor to measure the first measurement images on the first photoreceptor. The controller further controls the first image forming unit and a second image forming unit to form a plurality of measurement images while a rotation speed of the first photoreceptor is being controlled based on a measurement result of the first sensor, wherein the plurality of measurement images are formed along the predetermined direction of the intermediate transfer member.

An image forming apparatus includes an image bearing member, an exposure unit, a developing member, and a control unit. The exposure unit exposes a surface of the image bearing member to light to form an electrostatic latent image. The developing member develops the electrostatic latent image by using toner to form a toner image. In image formation based on input image data, the control unit uses the exposure unit to control a maximum gradation value of the toner image to be formed on the image bearing member surface, based on a repetition length of a dither pattern. The control unit performs control so that the maximum gradation value is larger in a case where a first dither pattern having a first length as the repetition length is used than where a second dither pattern having a second length longer than the first length as the repetition length is used.

Example implementations relate to a system comprising a memory resource to store instructions executable by a processing resource. In some examples, the processing resource can execute instructions to perform a calibration procedure for a printing device including a printing component. Responsive to the calibration procedure, the processing resource can execute instructions to deliver a print material arranged in a compound shape to a calibration image on the printing component included in the printing device. Responsive to performing the delivery, the processing resource can execute instructions to measure a print material density of the print material on the calibration image of the compound shape during the calibration procedure via a density sensor included in the printing device. Furthermore, the processing resource can execute instructions to detect an abnormality in the print material density via signal analysis instructions and provide a notification regarding the print material density abnormality.

Examples of methods are described herein. In some examples, a method includes calculating a first cost function measure based on band defects in an image. In some examples, the method also includes calculating a second cost function measure based on the band defects and a synthetic band. In some examples, the method further includes detecting a missing band based on a comparison of the first cost function measure and the second cost function measure.

An example image forming apparatus includes a printing engine including a plurality of photosensitive drums, a motor device to provide a driving force to each of the plurality of photosensitive drums, and a processor to control the printing engine such that printing data is printed on a printing paper and control the motor device such that at least one of the plurality of photosensitive drums operates at a different speed from the other photosensitive drums while the printing data is printed.

An example image forming apparatus includes a charger, a developing device, a sensor, and a controller. The charger may apply a plurality of charging voltages to a photoconductor, the plurality of charging voltages having different magnitudes and respectively corresponding to a plurality of area sections constituting a test pattern and the developing device may supply a developer to the photoconductor. The sensor may sense an image formed by the supplied developer and corresponding to the test pattern. The controller may determine a remaining lifetime of the photoconductor based on the image corresponding to the test pattern.

An image forming apparatus includes: an image processor configured to convert image data based on a first conversion condition; an image forming unit configured to form an image on a sheet based on the image data converted by the image processor, the image forming unit having an image bearing member on which the image is to be formed, a transfer unit configured to transfer the image from the image bearing member onto the sheet, and a fixing unit configured to fix the image to the sheet; a conveyance roller configured to convey the sheet having the image fixed thereto; a reading unit configured to read a pattern image on the sheet conveyed by the conveyance roller; a detector configured to detect a pattern image on the image bearing member.

An image forming apparatus includes an image bearing member, an image forming unit, a detection unit, and a control portion. The detection unit includes a casing, an optical sensor, a shutter portion, a moving member, a groove portion, and a projection portion. The optical sensor is disposed within the casing facing the image bearing member to detect the toner image and comprises a light emitting portion emitting light to the image bearing member through the opening portion and a light receiving portion receiving the light reflected from the image bearing member. The shutter is configured to open/close the opening portion as the projection portion moves in a direction intersecting with the predetermined direction as the moving member moves in the predetermined direction. The groove portion is disposed perpendicularly above an extension line of an optical axis of the light irradiated from the light emitting portion to the image bearing member.

There is provided an image forming apparatus in which an image carrier and an elastic body may be in pressure contact with each other, and in which a toner remover may be in contact with the image carrier to remove toner remaining on the image carrier. The image forming apparatus may include: a first hardware processor that forms an image pattern in a region including at least a part of a pressure contact part of the image carrier that is in pressure contact with the elastic body when operation of the image carrier is stopped; a second hardware processor that acquires density of the image pattern formed on the image carrier; a third hardware processor that adjusts driving time of the image carrier based on the density of the image pattern; and a fourth hardware processor that drives the image carrier for the driving time.

An image forming unit forms test images of a color of the same type as a first color using toner of a second color and toner of a third color, transfers a first and second test images, fixes the test images on a sheet, controls a sensor to read test images, determines sampling timings for the test images based on an output signal related to the first test image outputted from the sensor using a color filter of a fourth color, acquires a result of reading the test images based on a reading result of the test images on the sheet by the color sensor using a color filter of the first color, and the sampling timing, and determines a transfer voltage based on the result of reading the test images.