A print apparatus is disclosed. The print apparatus comprises a container-receiving unit for receiving a reusable print agent container; a print agent reservoir for storing print agent to be consumed by the print apparatus during a printing operation; a pump for transferring print agent between a reusable print agent container positioned in the container-receiving unit and the print agent reservoir; and processing circuitry. The processing circuitry is to operate the pump to transfer print agent of a first concentration from the reusable print agent container to the print agent reservoir; and, responsive to determining that a volume of print agent of the first concentration in the reusable print agent container has fallen below a threshold volume, operate the pump to transfer a volume of print agent of a second, lower concentration from the print agent reservoir to the reusable print agent container. A method and a machine-readable medium are also disclosed.

A method of calibrating a developer unit of a liquid electrophotographic printer, the method comprising: setting a developer roller voltage and iteratively printing a patch on a print medium using different electrode voltages until a hue of a patch printed using one of the electrode voltages is within a tolerance of a target hue; and setting an electrode voltage based on said one of the electrode voltages and iteratively printing a patch on a print medium using different developer roller voltages until a hue of a patch printed using one of the developer roller voltages is within the tolerance of the target hue.

A developing device includes a storage portion storing a developer, a conveying portion stirring and conveying the developer in the storage portion, a sensor, an acquisition processing portion, and a correction processing portion. The sensor outputs an electrical signal in accordance with magnetic permeability at a predetermined detection position in a conveyance path of the developer. The acquisition processing portion acquires a specific value based on the electrical signal outputted during a rotation period of the conveying portion. The correction processing portion corrects the specific value based on a rotation speed of the conveying portion when a fluctuation width of the electrical signal outputted during the rotation period of the conveying portion is less than a predetermined threshold, and corrects the specific value based on the rotation speed of the conveying portion and the fluctuation width when the fluctuation width is equal to or greater than the threshold.

Downtime relating to formation and detection of a detection image is reduced. An image forming apparatus includes a controller configured to calculate a first conversion unit to convert a gradation of input image data so that density output for the input image data becomes a first density output characteristic based on a first detection result of the detection image detected by a density sensor in a first mode. The controller generates a second conversion unit to convert the gradation of the input image data so that the density output for the input image data becomes a second density output characteristic in a second mode based on the detection result in the first mode and correction information, and further updates the correction information based on a second detection result of the detection image detected by the density sensor in the second mode and the first detection result.

A method of printing images in a liquid electrophotographic printer is provided. In an example, the method includes measuring at least one current associated with an image development unit of the liquid electrophotographic printer. A first time at which a peak occurs in the measured current is determined; the first time indicates that a printing substance is transferred from a point on a developer roller of the image development unit to a photo imaging member of the liquid electrophotographic printer at a first location within the image development unit. A second time at which said point on the developer roller is expected to contact the cleaner roller within the image development unit is calculated and, at the second time, a voltage applied to the cleaner roller is controlled to reduce the potential difference between the cleaner roller and the developer roller.

A toner transport apparatus includes a toner, a transport container having a transport path for transporting the toner toward the developing apparatus, and a pipe through which the toner is transported from the toner container to the transport container, with the pipe having an outlet hole from which the toner is discharged into the transport container. An air pump transports the toner from the toner container to the transport container, and an optical sensor includes a light-emitting element to emit a light and a light-receiving element to receive the light so that an optical path from the light-emitting element to the light-receiving element intersects with a passage area of the toner through which the toner passes after being discharged from the outlet hole of the pipe and before landing at a landing point of the transport container.

In one example of the disclosure, a first voltage is provided to an electrode of a development assembly during a first printing operation. The developer assembly includes a current-resistant coating and is to develop print fluid with conductive particles. Contemporaneous with the providing of the first voltage to the electrode, a second voltage is provided to a squeegee roller of the developer assembly. Data indicative of a measurement of optical density of a first image printed utilizing the developer assembly is received. During a second printing operation, if the measured optical density is outside a target optical density, contemporaneously the first voltage is provided to the electrode and a third voltage to the squeegee roller to adjust image optical density.

In an example, a method includes collecting (102) print agent from a print agent reservoir to form a print agent layer on a first print agent transfer member (204). The print agent layer may be transferred (104) directly from the first print agent transfer member to a second print agent transfer member (206), where the print agent layer may be heated (106). The print agent layer may be applied (108) directly from the second print agent transfer member to a substrate.

Downtime relating to formation and detection of a detection image is reduced. An image forming apparatus includes a controller configured to calculate a first conversion unit to convert a gradation of input image data so that density output for the input image data becomes a first density output characteristic based on a first detection result of the detection image detected by a density sensor in a first mode. The controller generates a second conversion unit to convert the gradation of the input image data so that the density output for the input image data becomes a second density output characteristic in a second mode based on the detection result in the first mode and correction information, and further updates the correction information based on a second detection result of the detection image detected by the density sensor in the second mode and the first detection result.

A print agent vessel is disclosed that comprises a circuit, the circuit comprising a first electrically conductive portion to couple to a first terminal of a printing device, a second electrically conductive portion to couple to a second terminal of the printing device, and an electrically conductive component capacitively coupled to the first electrically conductive portion. The circuit has a variable capacitance that is indicative of a parameter of the component.