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.
'Brightness/Color detail loss' specifies a measure of allowed acceptable detail loss in order to reduce noise.
This may be useful for manipulation of the image in the Layer module (for example subtracting the healed image from the original image).
If your data is very noisy, it is possible AutoDev will optimise for the noise, mistaking it for real detail.
This is often observable as "washing out" of coloring in the highlights.
StarTools' AutoDev module however uses image analysis to find the optimum custom curve for the characteristics of the data.
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