The Levels adjustment has three eyedroppers that relate to shadows, midtones and highlights and can warm up images in an instant
The Levels adjustment can be tweaked manually to create changes to lighting, but by using the eyedroppers you can create various effects depending on where you click.
Take for example this image. For the Shadows, we selected the windows in the buildings using the Eyedropper in the adjustment.
For the highlights, we went for the brightest part of the image – the sky between the clouds.
But for the midtones eyedropper, clicking on the grey clouds created an interesting yellow hue. However, a blue hue was created by clicking on some of the buildings.
This change in colour is a result of shifting RGB values, and by using the midtones eyedropper the colour and mood of an image can be quickly altered.