Remove Background

About the Remove Background filter

This filter can be found in the Filters menu, in the Astrophotography category.

A colour-sampling handle is precreated at the centre of the image. Drag it to reposition as needed to sample a background tone to be subtracted.

Use a single handle to remove a fairly uniform background. Click within the document view to create additional handles to remove gradients, e.g. caused by light pollution, sky glow or moon illumination.

Alternatively, specify your own grey and RGB levels for subtraction by selecting a handle and manually setting the filter's Grey, Red, Green and Blue values. Manually setting any of these values will cause Sample colour at handle to become deselected for the selected handle.

Settings

The following settings can be adjusted in the filter dialog:

Sample colour at handle—when selected (recommended), the grey and RGB levels for the selected handle are automatically read from the handle's position.
Radius—controls the distance from which colour is sampled around the handle, up to a maximum of 20 px. Type directly in the text box or drag the slider to set the value.
Grey—controls the level of grey to be subtracted from the image. Type directly in the text box or drag the slider to set the value.
Red—controls the level of red to be subtracted from the image. Type directly in the text box or drag the slider to set the value.
Green—controls the level of green to be subtracted from the image. Type directly in the text box or drag the slider to set the value.
Blue—controls the level of blue to be subtracted from the image. Type directly in the text box or drag the slider to set the value.
Output black level—prevents darker tones being clipped and provides control over the background's aesthetic. Type directly in the text box or drag the slider to set the value.

About the Remove Background filter

Settings

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