An encoder receives an input enhanced dynamic range (EDR) image and a corresponding lower dynamic range (LDR) image to be coded at a given target rate. Before coding, a pre-dithering process is applied to the input LDR image to generate a dithered LDR image at a second bit depth, lower than its original bit depth. The pre-dithering process includes: generating uniformly-distributed noise, applying a spatial filter to the noise to generate low-pass or high-pass filtered noise, applying a temporal high pass or low pass filter to the spatially-filtered noise to generate output noise, adding the output noise to the input LDR image to generate a noise-enhanced LDR image, and quantizing the noise-enhanced image to generate the dithered LDR image. Selecting the characteristics of the dithering filters is based on both the target bit rate and luminance characteristics of the pixels in the input LDR image.