To make a varying series of images appear more “consistently” exposed, select the images (making sure that the most properly exposed image is the “most selected”, and choose Settings > Match Total Exposures” in the Develop module. This command will look at the overall brightness and contrast (as well as some additional in-camera settings such as ISO and shutter speed settings) and attempt to match the series to the most selected image.
Command + Option (Mac) / Control + Alt (Win) + Shift + M will Match Total Exposures (the shortcut is available in both the Library as well as Develop Modules).
