What do the terms HDR image and LDR image mean?
LDR image stands for Low Dynamic Range image. The term refers to images whose data is saved in a ‘traditional’ image format. Formats like JPEG are very limited with respect to their presentable tonal value range. With the 8 Bits of data per color channel one can distinguish only 255 different tonal values. The presentable dynamic range, i.e. the ratio of highest to lowest possible intensity value is hence only 255 : 1. This dynamic range is far to small for lossless saving of scenes comprising both strong light sources and deep shadows. Such scenes can easily have dynamic ranges of 100,000 : 1 and more. HDR image stands for High Dynamic Range image. HDR images are stored in a format that can present a much broader range of intensity values per pixel and color channel compared to LDR image formats. Lossless storage of HDR images generated with FDRTools requires an according HDR image format. Examples of such HDR image formats are OpenEXR, Radiance RGBE and TIFF with 32 Bits per color ch
