The Histogram window enables you to diagnose and fix common exposure problems. The histogram’s undulating graph shows the spread and strength of particular tones, with shadows at the left, midtones in the middle and highlights at the right.
The histogram for our unprocessed start image has plenty of shadows at the left, but it lacks strong highlights at the far right. This indicates that the start file is slightly under-exposed.
After using Exposure Compensation to brighten up the shot, the edited image’s histogram graph has more highlights peaking at the far right. The shadows are less strong at the left, as they’ve been brightened up by the Shadow Protection slider in Step 3.