Steve Cannistra, Dark Halo Removal Dark halos around stars can result from overly aggressive use of deconvolution or unsharp masking.

Steve Cannistra, Dark Halo Removal Setting up the technique in Photoshop: 1. Duplicate the layer (Layer, Duplicate Layer). Smooth the top layer (Filter, Noise, Median). A radius of 5 is a good starting point. 3. Assign the top layer to “lighten” mode. 4. Create a top layer mask (Layer, Add Layer Mask, Hide All). 5. The layer should now look like this (next slide):

Steve Cannistra, Dark Halo Removal Lighten mode Original layer Mask Median smoothed layer

Steve Cannistra, Dark Halo Removal Removing the halos is accomplished by painting the mask white in the areas of affected stars: 1. Select the paint brush tool. Make certain color is set to white. Adjust the paint brush diameter so that it is approximately the same size as the stars. 3. Click on the black mask area to make it active. Paint over the affected stars to reveal the overlying lighter regions of the smoothed top layer. The dark halos around the stars should nicely fill in. 5. The layer should now look like this (next slide):

Steve Cannistra, Dark Halo Removal Final image with halos removed Mask with white areas representing locations of affected stars