An image forming apparatus, configured to operate in first and second modes of which color gamut is different from each other, includes an exposure unit configured to expose a photosensitive drum; a developing roller configured to form a toner image; a detection unit configured to detect density of the toner image transferred to an intermediate transfer member; and a controller configured to adjust the density based on a value of input image data. A dithering process for the controller's controlling of the exposure unit is different depending on whether the operation is in the first mode or the second mode, and in at least a part of the input image data, the density of the toner image formed by the dithering process in the first mode is higher than the density of the toner image formed by the dithering process in the second mode.

An image forming apparatus includes a frame, a drum cartridge mountable to the frame, and including a photosensitive drum and a drum memory in which drum identification information identifying the drum cartridge is stored, and a control unit including a main body memory in which the drum identification information is to be stored. The control unit reads out the drum identification information from the drum memory, determines whether the drum identification information read out from the drum memory coincides with the drum identification information stored in the main body memory, and enables to execute resister pitch measuring processing of measuring variations in printing pitch due to the photosensitive drum. In a case where it is determined that the drum identification information read out from drum memory coincides with the drum identification information stored in the main body memory, the control unit does not execute the resister pitch measuring processing.

In an image forming apparatus, when a first sheet and a second sheet are subjected to printing and the second sheet is being conveyed at a particular timing after a sheet sensor detected passage of a trailing end of the first sheet, and when a sheet interval between the first sheet and the second sheet is equal to or greater than a particular threshold interval, a controller positions first and second developing rollers to first and second separated positions, respectively, after developing of images to be transferred onto the first sheet has been completed, positions the developing rollers to be used for printing on the second sheet to respective contact positions, and starts developing images to be transferred on the second sheet. The controller is further configured to perform a color printing using both the first and second developing rollers, and a monochromatic printing using only the second developing roller.

An image forming apparatus includes: a first developing roller movable between a first contact position and a first separated position; a second developing roller movable between a second contact position and a second separated position; and a controller. When a sheet interval is shorter than a first interval and is longer than or equal to a second interval, the controller maintains the first developing roller at the first contact position even after the completion of its development for a preceding sheet, controls the first developing roller to start development for a subsequent sheet, moves the second developing roller to the second separated position after the completion of its development for the preceding sheet, moves the second developing roller again to the second contact position, and controls the second developing roller to start development for the subsequent sheet after the second developing roller is moved again to the second contact position.

An image forming apparatus includes a main body, endless belt, photosensitive drums, setting unit, contacting/separating mechanism, transmitting mechanism, and coupling members. The photosensitive drums are disposed in confrontation with the endless belt and are arranged in a first direction. Each photosensitive drum has an axis extending in a second direction perpendicular to the first direction. The setting unit sets the image forming apparatus to a monochrome mode or color mode. The contacting/separating mechanism controls at least one photosensitive drum to contact or separate from the endless in accordance with the set mode. The transmitting mechanism selectively transmits drive power to photosensitive drums. Each coupling member is selectively coupled to the corresponding photosensitive drum and has a coupling axis extending in the second direction. Each coupling member is uncoupled from the corresponding photosensitive drum when the contacting/separating mechanism controls the corresponding photosensitive drum to separate from the endless belt.

An image forming apparatus includes an image forming section, a driving unit and an operation unit. The image forming section includes one or more image forming units. The driving unit generates driving force. The operation unit selectively performs a first operation and a second operation. The first operation is an operation to change over from a coupled state of the one or more image forming units and the driving unit, which the driving force is transmitted to the one or more image forming units, to a released state of the one or more image forming unit and the driving unit, which the driving force from the driving unit is not transmitted to the one or more image forming units. When the second operation is performed, the released state is maintained.

An image forming apparatus includes a main body, a drum cartridge removably attached to the main body, and a belt unit removably attached to the main body. The main body includes a drum power supply, a belt power supply, and a controller configured to start supplying power from the drum power supply to a drum memory of the drum cartridge, start supplying power from the belt power supply to a belt memory of the belt unit, stop supplying the power from the drum power supply to the drum memory after starting supplying the power from the drum power supply to the drum memory, and stop supplying the power from the belt power supply to the belt memory after starting supplying the power from the belt power supply to the belt memory.

An image forming apparatus includes a plurality of photosensitive members; a scanner unit which includes light sources, a rotatable polygonal mirror, and a plurality of reflecting members; a fixing unit; and a discharge tray. The scanner unit is provided between the plurality of photosensitive members and the discharge tray with respect to a vertical direction, and a rotational axis of the rotatable polygonal mirror is inclined relative to the vertical direction. Selected ones of the laser beams emitted from the light sources are reflected toward a side with the fixing unit, and remaining ones of the laser beams are reflected toward an opposite side. Of the selected ones of the laser beams, the laser beam reflected toward the reflecting member provided at a position remotest from the rotatable polygonal mirror travels downward relative to a horizontal direction.

In an image forming apparatus, a first photosensitive drum is disposed upstream of a second photosensitive drum in a conveyance direction. Each of first and second developing rollers is movable between a contact position contacting a corresponding photosensitive drum and a separated position separated from the corresponding photosensitive drum. In a first case where a color print process is executed, a first moving mechanism starts moving the first developing roller toward the contact position, a manual feed roller starts picking up the sheet on a manual feed tray, and a second moving mechanism starts moving the second developing roller toward the contact position. In a second case where the monochrome print process is executed, the manual feed roller starts picking up the sheet on the manual feed tray, and the second moving mechanism starts moving the second developing roller toward the contact position.

An image forming apparatus includes: a first gear train including a first clutch; a second gear train including a second clutch; a third gear train including a third clutch; a fourth gear train including a fourth clutch; a motor including an output shaft; an output gear rotatable with the output shaft; a fifth gear train connected to the first and second clutches; and a sixth gear train connected to the third and fourth clutches. The first clutch engages transmission of a driving force to a first developing unit, the second clutch engages transmission of a driving force to a second developing unit, the third clutch engages transmission of a driving force to a third developing unit, and the fourth clutch engages transmission of a driving force to a fourth developing unit. The fifth and sixth gear trains are connected to the output gear independently from each other.