Radial masking is a powerful feature of Luminar and makes it easy to enhance or edit selective areas of your image, particularly if they are spherical. A great example of the use of the radial masking tool is that of highlighting the subject of your image, such as a face in a portrait, by separating it from the background. Another example might be to edit sunsets. This video about Luminar will show you how to properly apply a radial mask by clicking and dragging the "circle" and cover other techniques related to adjusting or enhancing the outer regions of the radial mask and the inner regions. You'll also see applications of layers and masks.
If you'd like to try this technique yourself, simply download a free, unlimited-time trial at skylum.com/luminar. Happy photo editing!