I’ve a sequence of photos that are vignetted – an artefact which I need to cut back from the photographs (see the smoothed and down-sampled picture).

My strategy is to subtract a heavily-smoothed model from the precise picture to take away the inhomongeious background brightness, nevertheless the outcomes of that had been removed from satisfactorily.
Altering the black level of the picture clearly doesn’t work both.

Is there a approach I miss to cope with such downside?

Info on the lens vignetting behaviour aren’t accessible past what I see on photos.

An strategy I can think about to work is to subtract a frequency-filtered model of the picture the place I solely retain the very low radial-symmetric frequencies from the unique, thus conserving the high-frequency content material of stars and galaxies intact. But I fail to search out any approach to take action protected than writing such plugin myself. Do I miss any strategy with gimp (or one other programme which I can get engaged on linux)?