Abstract: In an example, a method includes printing a set of images by transferring print agent between a roller of a print agent source and an electrophotographic surface in a plurality of transfer operations, wherein the roller is controlled to have a first voltage profile during each of the transfer operations. A variation in optical density which is consistent across the set of printed images may be detected, and a second voltage profile correction may be determined based on the variation in optical density. The method may further comprise printing a subsequent image by transferring print agent between the print agent source roller and the electrophotographic surface in a subsequent transfer operation, wherein the roller is controlled to have the second voltage profile during the subsequent transfer operation.

Abstract: In an example, a method includes printing a set of images by transferring print agent between a roller of a print agent source and an electrophotographic surface in a plurality of transfer operations, wherein the roller is controlled to have a first voltage profile during each of the transfer operations. A variation in optical density which is consistent across the set of printed images may be detected, and a second voltage profile correction may be determined based on the variation in optical density. The method may further comprise printing a subsequent image by transferring print agent between the print agent source roller and the electrophotographic surface in a subsequent transfer operation, wherein the roller is controlled to have the second voltage profile during the subsequent transfer operation.

Abstract: An example is provided to calculate calibration data for or print quality data of a printer, in one example, image data on printed elements of a plurality of patches printed at different powers or intensities by a print device may be determined.

Abstract: An example printer comprises an impression cylinder arranged to receive an impression medium thereon and an intermediate transfer member arranged to transfer printing fluid onto a substrate received on the impression medium. The printer further comprises an image sensor arranged to sense an accumulation of printing fluid on the impression medium as sensor data and a controller. The controller is configured to determine, based on the sensor data, an accumulation level of the printing fluid on the impression medium and determine if the accumulation level meets a threshold.

Abstract: An example is provided to calculate calibration data for or print quality data of a printer, in one example, image data on printed elements of a plurality of patches printed at different powers or intensities by a print device may be determined.

Abstract: Methods of measuring colors, methods of calibrating printers and printing systems for implementing the methods are disclosed. Calibration maps are printed on print media. The calibration maps have intertwined contiguous printed and non-printed areas. One or more color signals are measured on contiguous printed areas. One or more noise signals are measured on non-printed areas that are adjacent to the contiguous printed areas. Clear color signals are generated by removing the one or more measured noise signals from the one or more measured color signals.

Abstract: Methods of measuring colours, methods of calibrating printers and printing systems for implementing the methods are disclosed. Calibration maps are printed on print media. The calibration maps have intertwined contiguous printed and non-printed areas. One or more colour signals are measured on contiguous printed areas. One or more noise signals are measured on non-printed areas that are adjacent to the contiguous printed areas. Clear colour signals are generated by removing the one or more measured noise signals from the one or more measured colour signals.