- Additional HDR files are separate files of the complete project (two to three), such as a separate nebula, star foreground, and light sources-if they are not included in the star foreground or nebulae. I decided to include them for greater flexibility and easier adaptation to individual projects. *You can use a bitmap editor for editing, such as Photoshop, Affinity Photo, or any other that supports 32-bit working space. *Load all "Additional HDR files" into the editor. *The "Nebula" file should be placed at the bottom, and the "Stars" and "Light source" files at the top, both set to the 'Add' blend mode. *Now each layer can be edited separately-adjustments via exposure, and color grading using the channel mixer. *After making the desired corrections, export the result as HDR or EXR.