Image data is encoded for distribution in a lower bit-depth format. The image data has a range that is less than a maximum range and is mapped to the lower bit depth format using a mapping such that a ratio of a range of the lower bit depth representation to a maximum range of the lower bit depth representation is greater than a ratio of the range of the image data to a maximum range of the image data. Metadata characterizing the mapping is associated with lower bit depth representation. The metadata may be used downstream in combination with local dimming capabilities of a display to reverse the mapping so that tonal detail is better reproduced.