Bring out detail in images of nebulae
Transform your images of these faint targets from dark RAW captures using free software
Before: the workflow began with a TIFF file consisting of RAW images stacked in DeepSkyStacker
After: the final image processed in RawTherapee shows the Horsehead Nebula in all its iconic detail
zoom in to make adjustments, this window shows how changes will affect the whole picture. The main adjustment menus are located on the top right-hand side (as highlighted in Screenshot 1). The menu icons are, from left to right, ‘Exposure’, ‘Detail’, ‘Colour’, ‘Advanced’, ‘Transform’, ‘Raw’ and ‘Metadata’. We’ll focus on the first four menus for adjustments.
Bringing out details
Clicking on the ‘Exposure’ menu icon brings up submenus below it. These are used to increase the brightness of the image and boost the contrast between highlights and shadows, which will help bring out details. The ‘Exposure’ submenus include ‘Shadows/Highlights’. This submenu has a power symbol on the left, which means any changes made will only appear if the submenu is switched on by clicking this icon. Once the power symbol is clicked, the ‘Highlights’, ‘Shadows’ and ‘Radius’ sliders within the submenu to the right can be moved, and the nebulae start to appear as adjustments are made.
It’s worth noting that some submenus in ‘Exposure’, such as ‘Tone Mapping’, also have ‘1:1’ next to them. With these submenus you need to zoom in to see the changes made. This is achieved by clicking the ‘1:1’ icon at the bottom right of the image.
Further adjustments in the ‘Exposure’ menu are made by adjusting sliders in the ‘Tone Mapping’ and ‘L*a*b* Adjustments’ submenus. The ‘Tone Mapping’ functions are used to increase detail and structure in dark areas, while ‘L*a*b* Adjustments’ allows colour