When light comes from behind a subject, it can make the subject a bit dark. But it can also make for a strong contrast between your subject and its background. If you adjust the exposure so that the subject is properly lit, you risk making the background overexposed . To compensate for washed-out skies, sun-kissed lakes, and other light backgrounds in your images, use the Adjust Backlighting tool. It adjusts the midtones in the image, darkening the background without lightening the subject too much.
You can select an area if you want your changes to affect only that portion of the image; then choose Enhance, Adjust Lighting, Adjust Backlighting. Drag the Darken slider to the right until the background is no longer washed out; then click OK.
The Fill Flash tool has almost the opposite effect; it adds light to the subject, just as a camera flash would. Again, in backlit situations, a subject can become too dark and lose detail. This tool helps to compensate for that. Select an area to affect if desired; then choose Enhance, Adjust Lighting, Fill Flash. Drag the Lighter slider to the right until you can see some detail in the subject. Because this effect might wash out the subject too much, bring up the colors by adjusting the Saturation levels. When you're satisfied, click OK.