Abstract: In one example of the disclosure, an uncalibrated sensor may be calibrated. Calibrated sensor data is obtained. The data relates to an amount of light transmitted through an ink solution of a first colour as a function of ink concentration. An amount of light transmitted through an ink solution of the first colour is measured, using the uncalibrated sensor, at a plurality of ink concentrations. A calibration factor relating the light transmission of the calibrated sensor for the first colour and the light transmission of the uncalibrated sensor for the first colour is determined, using a processor, based on the obtained data and the measurements.

Abstract: In one example of the disclosure, an uncalibrated sensor may be calibrated. Calibrated sensor data is obtained. The data relates to an amount of light transmitted through an ink solution of a first colour as a function of ink concentration. An amount of light transmitted through an ink solution of the first colour is measured, using the uncalibrated sensor, at a plurality of ink concentrations. A calibration factor relating the light transmission of the calibrated sensor for the first colour and the light transmission of the uncalibrated sensor for the first colour is determined, using a processor, based on the obtained data and the measurements.

Abstract: In one example, a liquid electro photographic printing apparatus includes: multiple base color ink containers each to contain a different base color ink; multiple base color ink dispersion units each connected to a corresponding base color ink container to contain a diluted base color ink and to a corresponding base color binary ink developer unit; and a custom color ink container connected to each of the base color ink containers or to each of the base color ink dispersion units, to contain and mix a custom color ink, and connected to a custom color ink binary developer unit. The printing apparatus is configured to print any of the custom and base color inks using the custom color ink binary developer unit and the base color binary ink developer units.

Abstract: In one example, a liquid electro photographic printing apparatus includes: multiple base color ink containers each to contain a different base color ink; multiple base color ink dispersion units each connected to a corresponding base color ink container to contain a diluted base color ink and to a corresponding base color binary ink developer unit; and a custom color ink container connected to each of the base color ink containers or to each of the base color ink dispersion units, to contain and mix a custom color ink, and connected to a custom color ink binary developer unit. The printing apparatus is configured to print any of the custom and base color inks using the custom color ink binary developer unit and the base color binary ink developer units.

Abstract: A printing apparatus comprising a plurality of base color ink containers, each for containing a different base color ink, and a custom color ink container for containing a custom color ink, the printing apparatus being configured to print any of the custom color ink and the different base color inks, from the custom color ink container and the plurality of base color ink containers, respectively, to a print medium. The printing apparatus is configured to mix a custom color ink for the custom color ink container using a combination of any of the base color inks.

Abstract: A printing apparatus comprising a plurality of base color ink containers, each for containing a different base color ink, and a custom color ink container for containing a custom color ink, the printing apparatus being configured to print any of the custom color ink and the different base color inks, from the custom color ink container and the plurality of base color ink containers, respectively, to a print medium. The printing apparatus is configured to mix a custom color ink for the custom color ink container using a combination of any of the base color inks.

Abstract: A method and apparatus to calculate the optical density of a fluid (110) traveling through a narrow gap (30) with a set width. Typically, a densitometer employs a light source (10) that is configured to transmit light across the gap and a detector, opposite the light source (10), configured to detect light transmitted from the light source, across the gap, for calculating the optical density of the fluid. The apparatus and method further include a transparent element (120), the transparent element part of a set of replaceable transparent elements, each replaceable transparent element having a particular width, the width less than the width of the gap. Typically, the transparent element is moved into the gap between the light source and the detector to narrow the effective sampling width of the gap for calculating the optical density of the fluid. In some examples, the transparent element is further configured to rotate in the gap to enhance the flow of the fluid through the gap.

Abstract: A method of calibrating an optical density sensor comprising calculating a first pigment solid density value of an ink solution using a current first electrical output signal value from a photodetector, a current second electrical output signal value from a photodetector, and a current lens gap value, calculating a second pigment solid density value of the ink solution using a previously measured first electrical output signal value, a previously measured second electrical output signal value, and a previously measured lens gap value, comparing the current first electrical output signal value, the current second electrical output signal value, and the current lens gap value with the previously measured first electrical output signal value, the previously measure second electrical output signal value, and the previously measured lens gap value, and comparing the first pigment solid density value with the second pigment solid density value.

Abstract: A method and apparatus to calculate the optical density of a fluid (110) traveling through a narrow gap (30) with a set width. Typically, a densitometer employs a light source (10) that is configured to transmit light across the gap and a detector, opposite the light source (10), configured to detect light transmitted from the light source, across the gap, for calculating the optical density of the fluid. The apparatus and method further include a transparent element (120), the transparent element part of a set of replaceable transparent elements, each replaceable transparent element having a particular width, the width less than the width of the gap. Typically, the transparent element is moved into the gap between the light source and the detector to narrow the effective sampling width of the gap for calculating the optical density of the fluid. In some examples, the transparent element is further configured to rotate in the gap to enhance the flow of the fluid through the gap.

Abstract: A method of calibrating an optical density sensor comprising calculating a first pigment solid density value of an ink solution using a current first electrical output signal value from a photodetector, a current second electrical output signal value from a photodetector, and a current lens gap value, calculating a second pigment solid density value of the ink solution using a previously measured first electrical output signal value, a previously measured second electrical output signal value, and a previously measured lens gap value, comparing the current first electrical output signal value, the current second electrical output signal value, and the current lens gap value with the previously measured first electrical output signal value, the previously measure second electrical output signal value, and the previously measured lens gap value, and comparing the first pigment solid density value with the second pigment solid density value.