First of all, thanks a lot, @afre ! I am curious to see what your Gleam Filter does!
As long as I don’t have it, I’ll try to explain it in more detail, what I find interesting, if this would be possible:
What I find very elegant when editing photos is to try to direct the eye of the viewer to the subject by soft illumination of certain areas.
This can be done by intensifying the already existing illumination or by “artificially” illuminating it (which you could achieve, for example, when photographing with flash and softbox).
Digitally, one can try to imitate this with the help of Dodge and Burn technique. Depending on the subject, this can be very tedious. You have to make sure that the light is distributed in such a way that it looks realistic.
Let’s illustrate this with an example:
In this picture the forest is well lit. And we have hiker who enjoy this view but it is in the shadows. I would like to bring the area with her a little bit more into focus by soft illumination.
I can do this in the GIMP by painting the areas on a new transparent layer with the white brush and then…
…use soft light blend mode to illuminate the lower layer:
Well, what I liked about the Relief Light Filter by @David_Tschumperle , the illumination takes into account to some extent the distribution of light in light and shadow areas (here the example is exaggerated to make it clear):
Now, if I de-saturate this layer and remove black, I have a layer to lighten the area:
With soft light blend mode, I get a nicely illuminated area that looks natural:
If I also apply the Gaussian blur to this layer, I get even smoother transitions of light and shadow:
