Star reduction for astrophotography

[Gru]

Hey guys,

by using photoshop it was easy to reduce stars. You just select the highlights, expand the radius, convert into a smart object and make the shadows.

How can I do this in Affinity Photo?

My first steps are:

Select Highlights and expand the range circular.

and then?

 

Thank you for advice!

[James Ritson]

Hi @Gru, I'm not familiar with the end step—make the shadows?

Do you mean the content aware replacement once you have your stars selected? I usually do:

• Select>Tonal Range>Select Highlights
• Select>Grow/Shrink (somewhere between 6-12px)
• Select>Smooth (optional, depending on image)
• Edit>Inpaint

The last step will inpaint all the selected stars out and typically replace them with dark sky detail.

Other things you may want to try:

• Duplicate your pixel layer (e.g. Background), go to Filters>Sharpen>Clarity and use a negative value, then apply the filter. Change the layer opacity to alter the strength of the star removal.
• Select>Select Sampled Colour: useful for selecting dimmer stars, especially if they have colour fringing (e.g. red/purple). Similar procedure to the inpainting technique mentioned above.
• Layer>New Live Filter Layer>Blur>Minimum Blur, or alternatively use the destructive Filter menu version on a duplicated pixel layer. Mask away from the important areas like your deep sky objects to ensure you don't remove too much information.

Hope that helps!

[Gru]

Hey James,

thank you very much for your answere.

Your tips:

• The Inpaint does not help so good and gave many artifacts.
• The clarity filter works perfect! From a glossy star field to a great picture in wide field photos.
• Sample colour as you said. For dimming stars with a specific colour from cromatic abberation e.g.
• The minimum blur also is not working for me. In a range between 0.1 and 1.2 pixel the filter doesn´t even work. After 1.3/1.5 pixels the effect is way too crazy

Christian

[innerside]

On 8/7/2020 at 6:36 PM, James Ritson said:

Duplicate your pixel layer (e.g. Background), go to Filters>Sharpen>Clarity and use a negative value, then apply the filter. Change the layer opacity to alter the strength of the star removal.

For me this one works perfectly. Such a simple but strong schema of using negative clarity! Thanks James!