The graduated filter tool is Lightroom is extremely useful for landscape and nature photography. You can use this tool in a similar way that you would use a graduated neutral density filter on a lens, to balance out the exposure of the image. It’s common to have a scene where the sky is much lighter/brighter than a dark foreground, and Lightroom’s graduated filter can really make a big difference by balancing out that exposure.
The problem with the graduated filter, or even a graduated neutral density filter attached to your lens, is that the gradient is totally linear, and the subjects of your landscape photos will very rarely involve only straight lines. For example, there will often be trees, mountains, cliffs, or even man-made structures that jut into the sky in your photos. If you are using a graduated filter to darken the sky you will wind up darkening everything above the horizon, including things like trees that you may not want to darken. Also, the horizon is rarely perfectly straight.
Related video: How to Use Lightroom’s Graduated Filter
Fortunately, in Lightroom it is very possible to customize the effects of a graduated filter so that it only impacts the right parts of your photos. The end result is a much more natural look, rather than being very obvious that you used the filter.
In this video Simon Plant demonstrates how to brush out certain parts of the graduated filter to get this customized effect.
If you don’t already have Lightroom you can download a free trial here.