Apparatus comprising: a pixel coordinate mapping unit configured to transform image data according to a parameterized transfer function characterized by a plurality of anchor points and a free parameter, the parameterized transfer function having a mid-range slope controlled by the free parameter, wherein transformations at the anchor points are not affected by the free parameter; wherein the anchor points comprise black level and white level anchor points and a mid-tone anchor point, the black level anchor point corresponding to a transformation from a black level of a color-timing display used in color-timing or approving the image data to a black level of the target display used for display of the transformed image data, the white level anchor point corresponding to a transformation from a white level of the color-timing display to a white level of the target display; wherein the mid-tone anchor point affects a target brightness of the image data on the target display; wherein the black level of the color-timing display differs from the black level of the target display and/or wherein the white level of the color-timing display differs from the white level of the target display; wherein the apparatus is configured to receive metadata associated with the image data, the metadata carrying information about the color-timing display; wherein the apparatus is configured to determine values for the plurality of anchor points of the parameterized transfer function using the information about the color-timing display carried in the received metadata and information about the target display; wherein the black level anchor point is determined so as to have the black level of the color-timing display as its horizontal coordinate and the black level of the target display as its vertical coordinate; and wherein the white level anchor point is determined so as to have the white level of the color-timing display as its horizontal coordinate and the white level of the target display as its vertical coordinate. a pixel coordinate mapping unit configured to transform image data according to a parameterized transfer function characterized by a plurality of anchor points and a free parameter, the parameterized transfer function having a mid-range slope controlled by the free parameter, wherein transformations at the anchor points are not affected by the free parameter; wherein the anchor points comprise black level and white level anchor points and a mid-tone anchor point, the black level anchor point corresponding to a transformation from a black level of a color-timing display used in color-timing or approving the image data to a black level of the target display used for display of the transformed image data, the white level anchor point corresponding to a transformation from a white level of the color-timing display to a white level of the target display; wherein the mid-tone anchor point affects a target brightness of the image data on the target display; wherein the black level of the color-timing display differs from the black level of the target display and/or wherein the white level of the color-timing display differs from the white level of the target display; wherein the apparatus is configured to receive metadata associated with the image data, the metadata carrying information about the color-timing display; wherein the apparatus is configured to determine values for the plurality of anchor points of the parameterized transfer function using the information about the color-timing display carried in the received metadata and information about the target display; wherein the black level anchor point is determined so as to have the black level of the color-timing display as its horizontal coordinate and the black level of the target display as its vertical coordinate; and wherein the white level anchor point is determined so as to have the white level of the color-timing display as its horizontal coordinate and the white level of the target display as its vertical coordinate.