A method of producing a printed output on a substrate using a drop emitting device adapted to emit a plurality of ink drops per pixel in response to a control signal, the method comprising the steps of: a. receiving (210, 310) image data corresponding to a pixel of an image to be printed, the received image data comprising a tone value (C r); b. generating (220, 320) a threshold value for the pixel for use in a screening operation by looking up a threshold value from a threshold array using the location of the pixel within the image to be printed; characterised in that the method further comprises: c. mapping (230, 340) the received tone value (C r) to a mapped tone value (C m) using a tone mapping, the mapped tone value representing a specific tone within a predetermined range of tones and being generated based on the received tone value; d. performing the screening operation by comparing (250, 350) the mapped tone value (C m) with the threshold value; and either e. mapping (260; 360) the received tone value (C r) to a control signal value controlling the number of drops of ink emitted from the drop emitting device for the pixel using a control mapping if the outcome of the comparison performed in previous step (d) is that the threshold value is greater than or equal to the mapped tone value (C m), the control signal value being generated based on the received tone value (C r); or f. repeating steps (c) and (d) if the outcome of the comparison performed in previous step (d) is that the threshold value is less than the mapped tone value (C m), wherein in each repetition of step (c) the tone mapping is altered by using a different tone mapping so that the received tone value is mapped to an alternate mapped tone value and wherein steps (c) and (d) are repeated either: until the outcome of the comparison performed in step (d) is that the threshold value is greater than or equal to the mapped tone value; or, until a predetermined number of repetitions has been performed with the threshold value being less than the mapped tone value (C m), thereafter step (e) is performed wherein the control mapping is altered so that the received tone value is mapped to an alternate control signal value which is based on the received tone value and the number of repetitions of steps (c) and (d). a. receiving (210, 310) image data corresponding to a pixel of an image to be printed, the received image data comprising a tone value (C r); b. generating (220, 320) a threshold value for the pixel for use in a screening operation by looking up a threshold value from a threshold array using the location of the pixel within the image to be printed; c. mapping (230, 340) the received tone value (C r) to a mapped tone value (C m) using a tone mapping, the mapped tone value representing a specific tone within a predetermined range of tones and being generated based on the received tone value; d. performing the screening operation by comparing (250, 350) the mapped tone value (C m) with the threshold value; and either e. mapping (260; 360) the received tone value (C r) to a control signal value controlling the number of drops of ink emitted from the drop emitting device for the pixel using a control mapping if the outcome of the comparison performed in previous step (d) is that the threshold value is greater than or equal to the mapped tone value (C m), the control signal value being generated based on the received tone value (C r); or f. repeating steps (c) and (d) if the outcome of the comparison performed in previous step (d) is that the threshold value is less than the mapped tone value (C m), wherein in each repetition of step (c) the tone mapping is altered by using a different tone mapping so that the received tone value is mapped to an alternate mapped tone value and wherein steps (c) and (d) are repeated either: until the outcome of the comparison performed in step (d) is that the threshold value is greater than or equal to the mapped tone value; or, until a predetermined number of repetitions has been performed with the threshold value being less than the mapped tone value (C m), thereafter step (e) is performed wherein the control mapping is altered so that the received tone value is mapped to an alternate control signal value which is based on the received tone value and the number of repetitions of steps (c) and (d). until the outcome of the comparison performed in step (d) is that the threshold value is greater than or equal to the mapped tone value; or, until a predetermined number of repetitions has been performed with the threshold value being less than the mapped tone value (C m), thereafter step (e) is performed wherein the control mapping is altered so that the received tone value is mapped to an alternate control signal value which is based on the received tone value and the number of repetitions of steps (c) and (d).