Steve Cannistra, Dark Halo RemovalSteve Cannistra, Dark Halo RemovalSteve Cannistra, Dark Halo RemovalSteve Cannistra, Dark Halo Removal

Dark halos around stars can result from overly aggressiveDark halos around stars can result from overly aggressive

use of deconvolution or unsharp masking.use of deconvolution or unsharp masking.

Steve Cannistra, Dark Halo RemovalSteve Cannistra, Dark Halo RemovalSteve Cannistra, Dark Halo RemovalSteve Cannistra, Dark Halo Removal

Setting up the technique in Photoshop:Setting up the technique in Photoshop:

1. Duplicate the layer (Layer, Duplicate Layer).1. Duplicate the layer (Layer, Duplicate Layer).

2.2. Smooth the top layer (Filter, Noise, Median). A radius of 5Smooth the top layer (Filter, Noise, Median). A radius of 5

is a good starting point.is a good starting point.

3. Assign the top layer to “lighten” mode.3. Assign the top layer to “lighten” mode.

4. Create a top layer mask (Layer, Add Layer Mask, Hide All).4. Create a top layer mask (Layer, Add Layer Mask, Hide All).

5. The layer should now look like this (next slide):5. The layer should now look like this (next slide):

Steve Cannistra, Dark Halo RemovalSteve Cannistra, Dark Halo RemovalSteve Cannistra, Dark Halo RemovalSteve Cannistra, Dark Halo Removal

Lighten modeLighten mode

MaskMask

Median smoothed layerMedian smoothed layer

Original layerOriginal layer

Steve Cannistra, Dark Halo RemovalSteve Cannistra, Dark Halo RemovalSteve Cannistra, Dark Halo RemovalSteve Cannistra, Dark Halo Removal

Removing the halos is accomplished by painting the maskRemoving the halos is accomplished by painting the mask

white in the areas of affected stars:white in the areas of affected stars:

1. Select the paint brush tool. Make certain color is set to white.1. Select the paint brush tool. Make certain color is set to white.

3. Click on the black mask area to make it active.3. Click on the black mask area to make it active.

2.2. Adjust the paint brush diameter so that it is approximatelyAdjust the paint brush diameter so that it is approximatelythe same size as the stars.the same size as the stars.

4.4. Paint over the affected stars to reveal the overlyingPaint over the affected stars to reveal the overlyinglighter regions of the smoothed top layer. The dark halos lighter regions of the smoothed top layer. The dark halos

around the stars should nicely fill in.around the stars should nicely fill in.

5. The layer should now look like this (next slide):5. The layer should now look like this (next slide):

Steve Cannistra, Dark Halo RemovalSteve Cannistra, Dark Halo RemovalSteve Cannistra, Dark Halo RemovalSteve Cannistra, Dark Halo Removal

Mask with white areasMask with white areasrepresenting locations ofrepresenting locations ofaffected starsaffected stars

Final image with halos removedFinal image with halos removed