1. A method for displaying an image for a target display comprising: receiving the image and associated metadata, the metadata identifies a source gamut of a reference display used for the image; in response to the receiving of the metadata, mapping a predetermined mid-tone image value for the reference display to a predetermined target display value, the mapping based on a sigmoidal function of L OUT = c 1 + c 2 ⁢ L IN n 1 + c 3 ⁢ L IN n , and adjusting the mapping in response to ambient lighting, the adjusting comprises increasing a target display value to which the predetermined mid-tone image value is mapped in response to an increase in the ambient lighting, wherein L OUT is an output of the mapping, L IN is an input of the mapping, and c 1 , c 2 , c 3 and n are numeric parameters, and wherein a dynamic range of the reference display differs from the target display.