The healing brush in Lightroom repairs imperfections using pixels from another part of the image. The same function existed in Photoshop for a long time. The coolest thing about this Lightroom feature is that when you use the healing brush to click on the spot you want to repair, it automatically pick a sample area for you. If you are not happy about it, you can move around and find your perfect spot to sample. You can also adjust the brush size anytime during the process to get the best result.

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Hope you enjoy the tutorial. Cheers.