The HDR module optimises local dynamic range allocation for smaller details (e.g. on a more local level) than the Contrast module; the HDR module works primarily medium-to-small features in the image.
The HDR module complements the Sharpen module and is generally a more flexible and powerful alternative that generally achieves artifact-free results. Examples of use cases are bright galaxy cores where small detail is still recoverable in the highlights.
The HDR module does not exacerbate noise grain like simpler dynamic range algorithms, factoring in noise propagation into the size of the final detail enhancement. As such, it is meant after your non-linear dataset has been stretched, for example using the Development or AutoDev modules.
As with most modules in StarTools, the HDR module comes with a number of presets;
Going beyond the presets, more detailed adjustments can be made, starting with the 'Detail Size Range' parameter. This parameter is highly influential on the end result. It governs the range of detail sizes HDR should concentrate on, in order to bring out the most detail. Keeping this value small will see small detail accentuated. However, using larger values will see both small and large structural detail modified. Using larger values will progressively dig out larger scale structures and can be quite effective in highlighting these.
A selection of different algorithms to bring out detail exists. These are chosen through the 'Algorithm' parameter;
In order to throttle how much the shadows and highlights respond to the enhancements, a brightness mask is used, the power of which is controlled by the 'Dark/Bright Response' parameter.
There is no exaggerated noise grain, just enhanced detail; objectively better results, in less time, with less hassle.
This time set 'Old Mask' to 'Add New To Old' to add the newly generated mask to the mask we already have.
Oversampling (meaning the finest detail, such as small stars, being "smeared out" over multiple pixels).
Most modules come with presets that quickly dial in useful parameter settings.
Any decisions you make affecting your detail does not affect the colouring of said detail, and vice-versa.
You can convert everything you see to a format you find convenient. Give it a try!