You may be wondering, what about Fill Light? Fill Light is an important slider just above Blacks. It helps bring out the darkest detail in the image. However, you have to be very careful in using it. As you increase its setting, the image can start to have an unnatural-looking balance of dark tones because the darkest tones get too bright before the less dark tones do. In addition, Darks does a better job of bringing out the best of all dark tones and colors with a nice blending among them for a more natural look.
Another option is judicious use of the Adjustment Brush in Lightroom and Camera Raw. I find it works best, when lightening dark areas, to set it to plus Exposure. I'll usually set it too high to start so I can better see the adjustment as it's painted on. Then I tone it back to a normal level when done.
Great darkroom workers used to talk about luminosity in a print. This referred to how lively the tones looked throughout the image, from dark to light. This is definitely possible with digital images, but the straight-from-the-camera image rarely will give you this. Just a little effort working on that image to clear up the dark tones can make a big difference in the final photo.
How (And Why) To Set Your Black Point
Digital cameras don't automatically give you an image with the best blacks. There are a number of reasons for this, though it partly has to do with lifting dark tones in a digital file because digital cameras can have trouble there. When blacks (meaning all the areas of pure black) in a photo aren't black, an image won't print or display with the best contrast, tonality or color. While some images won't have blacks (such as a foggy day), most do and need them in the photo.
Setting blacks is very visual with Adobe products. Start with the left, black slider of Levels in Photoshop products. For Lightroom and Camera Raw, use the Blacks slider in Basic. Important: Hold down Alt or Option as you click and move the slider.
The Blacks Threshold screen will appear, showing pure blacks against white when you get a pure black. Maxed-out color channels on the dark end appear as colors. You usually want at least some black to show up. If your image is filled with color, this might mean adjusting until areas of color show up.
A pure white screen means you're not using the entire range of tonality an image is capable of for most media. Use Fill Light to open dark areas slightly, but mainly use the Tone Curve.
Check your whites. With Adobe products, use the Alt or Option key with the white or right slider in Levels for Photoshop or the Exposure slider in Lightroom or Camera Raw to see a Whites Threshold screen. Usually, you barely want a white or color to show. I find that you have to be especially careful with Lightroom doing this, and sometimes seeing the whites in the Threshold screen goes too far.
Never use the black or white eyedropper in Levels if you're a nature photographer. That will remove important color casts that are usually a key part of outdoor images; plus, the eyedroppers adjustment is very heavy-handed. Seeing the blacks and whites with a Threshold screen is much better.
You can see more of Rob Sheppard's photography, find his book and learn about his workshops on his website, robsheppardphoto.com.