Learn how to fine tune sharpening with the Amount and Radius Sliders
The Detail panel in Lightroom controls sharpening on the image. Use the Amount slider to manage the intensity of the sharpening – set this to a high value to begin.
The Radius slider adds halos around the edges in the image which is what gives the sharpening effect.
For an image with lots of fine lines and detail such as a building select a low radius. For a portrait or an image with softer detail, use a high radius value.
Hold the Alt key (Option on the Mac) as you drag on the Radius slider to see the halos.