How to manually remove dust bunnies with Photoshop CS5 Content Aware Fill
OK, so you have taken your long exposure images and stacked ’em all up only to find you have big black holes in your image! These are tiny pieces of dust on one of the glass surfaces which block the light hitting the CCD Sensor. The BEST way to deal with these is with FLAT files – these are images taken of a uniformly white/grey scene taken without moving the anything in the image train. These flat files will show up the ‘Dust Bunnies’ as they are known and by using these images you can correct and repair the image. BUT…. say something goes wrong, you don’t have enough time to take flats (BTW, look back shortly for a tutorial on taking Flats), you move the CCD and the flats don’t work… Is there another way?
Thankfully there is! – Photoshop CS5 Content Aware Fill to the rescue!!!!
In Photoshop CS5 there is a new feature named content aware fill. This is really intended to remove lampposts and signs and things like this from normal daytime photographs but it does a fantastic job of removing dust bunnies from long exposure images. One caveat……. Content Aware works by sampling the surrounding area and replacing the selection with what it ‘thinks’ should be there. So, if you are looking for astronomically correct images, this process may not be for you as it could, potentially remove or add an extra star from the image. So… with that out of the way, how do you do it?
OK, First off, open your image in Photoshop CS5 and look at select the dust bunnies with the standard lasso selection tool
Once you have drawn a circle round your dust bunny – It does not have to be accurate BTW, very rough is fine, Press Shift & F5 (or from the Edit menu, select Fill). In the screen that pops up, drop down the ‘Use’ box and select ‘Content Aware’, then click OK and be amazed!
Here’s an example, I have drawn round a couple of the offending bunnies with a brush tool.
Here is the full image, showing the dust bunnies before and after removal – I think you will agree Photoshop has done a good job?
Here’s the image, after removing the bunnies