Every photographer who has used interchangeable lenses has faced this inherent problem with sensors exposed to the elements at least once: spots on the skies due to dust on the sensors. Digital technology has significantly lightened the means for the photographic production chain, but it must be said that with film, dust on the film was carried over to the next shot, and the problem really only arose on rare occasions.
Some spots are easy to detect, but it’s easy to overlook others. That’s where a devilishly handy little trick comes in: using an excessively tortured custom curve.
Indeed, this method enhances low contrasts, and where you previously saw nothing, new imperfections will then appear. It is then easy to finish the job by dabbing away the remaining blemishes.
Note that this technique is not limited to Lightroom; it works with any software that allows you to revert changes to the curves without erasing your work on the spots.