1. A method of producing a printed output on a substrate using a drop emitting device adapted to emit a plurality of ink quantities in response to a control signal, the method comprising the steps of: a. receiving image data corresponding to a pixel of an image to be printed, the received image data comprising a tone value; b. generating a threshold value for use in a screening operation based on the location of the pixel within the image to be printed; c. mapping the received tone value to a mapped tone value using a first tone mapping, the mapped tone value being generated based on the received tone value; d. performing the screening operation by comparing the mapped tone value with the threshold value; e. mapping the received tone value to a control signal value using a first control mapping if the output of the comparison performed in previous step (d) indicates a first relationship, the control signal value being generated based on the received tone value; and f. repeating steps (c) to (f) if the output of the comparison performed in previous step (d) indicates a second relationship, wherein step (c) comprises using an alternate tone mapping and step (e) comprises using an alternate control mapping.