From
this. To this. 
 If you are trying to get rid of light pollution in your images then a little trick I learnt that may come in handy. |
|
 |
First load your image use either File/Open or CTRL+O. Then open the File/Window/Layers dialog box (CTRL + L) |
 |
Under Layer choose Dupicate layer. |
 |
Now click Filters and come down to Blur/Gaussian Blur. |
 |
When the dialog box opens change it from 5 to around 50-70 and click OK. |
 |
Now move to the Layer box and change the Normal to Subtract. |
 |
Now move the slider to the left until you are happy with the result. |
 |
Click Image/Merge Visible Layers or CTRL+M to merge the 2 layers of your image. |
 |
Click OK at the next dialog box. |
 |
Now your image should be a little darker and perhaps a little sharper too. |
 |
To save your image use File/Save As or Shift+CTRL+S All the above can also be done with right mouse clicking on your image and the Layer dialog box and choosing the relevent headings. |