Despeckle

Digital images created by scanning small older photographs often suffer from conspicuous dust and scratches. The GIMP has a filter to correct this problem but as usual the filter should be used with moderation for it also causes the photograph to lose some fine detail. The dust in the following picture (the sun setting behind one of my students in Borneo) is very conspicuous against the smoothly graduated colours of the sunset.

Choose Filters>Enhance>Despeckle and then play with the settings to achieve the best reduction of dust without affecting the student's lovely profile. Start with adaptive=on, recursive=off, radius=2, black level= 4 and white level = (not very important here). Expand the preview window by dragging its lower right corner and switch the preview on and off to see what effect your settings are having on the image.

Also try these settings: adaptive=on, recursive=on, radius=15, black level=-1, white level = (not very important here). You can get a spectacular reduction in dust and scratches with the following settings but at the expense of an excessive loss of detail and an artifact at the bottom of the picture (note that Recursive is on):

The radius determines how far the filter searches for differences among pixels, so use the smallest radiusvalue that still has a good effect on reducing the dust defects. (Increasing the radius makes the image blurry.)

Save your work, and don't worry if some defects remain after your restrained use of the Despeckle filter - there is another way of tackling the worst defects: the clone tool. This is actually a very interesting tool, useful in many contexts in addition to this one. The clone tool copies parts of the image into neighboring parts using a brush.

First, select the clone tool in the main GIMP window by clicking it. Check that the tool's options (in the dialog below the toolbox) show that 'image source' and 'alignment=aligned' are selected. If the brush dialog box is not visible then display it with Dialogs>Brushes or Shift+Ctrl+B.

Before you continue, find out for yourself the difference between 'aligned' and 'non-aligned' in the options of the clone tool. Set the option back to 'aligned' before continuing.

Now that you have had some practice with the clone tool, try using it to turn this left photo from Bali, Indonesia into the photo on the right...

First, of course, you'll have to find the two differences between the two images...

I cheated a bit and used, in addition to the clone tool, the Blur/Sharpen tool to sharpen the parts of the image that I had worked on. This might also be a good time to try the smudge tool , but I think you'll find the clone tool more satisfying to use. See the GIMP help pages for advice in using the blur and sharpen tool and the smudge tool.

As usual, save your work when you're done.