Camera Raw Tone Curve

Tone Curve Dialog

Navigate to the Tone Curve dialog box in the right hand side of Camera Raw. In this exercise we will use the Parametric tab option. This will give us our curves similar to the curves adjustment layer in photoshop. It shows us our tonal range for the current image and contrast via the histogram displayed.
The Parametric gives you four catagories to work with. Highlights, Lights, Darks and Shadows.

Boundaries

You can control the boundaries of your histogram by sliding the sliders just below the histogram to the left or the right. In this case pulling the right triangle slider to the right a little more to meet the end of the histogram will bring in some more tonal values in the lighter areas.

Main Sliders

Now you have the ability to adjust each slider to control your tonal values. Highlights works with the top of the slope and adjusts your highs. Lights is basically working with mid tone tonal values and darks is working with the lower part of the spectrum. By draggin a slider to the right for any four of these, you will bring more light into that area of the histogram. By draggin to the left you will lower the amount of light. An example of this is shown on the slider bar itself just for reference (a gradient). The shadows slider is the very darkest part of the image.

Turn on Clipping

A good idea to do while adjusting these sliders is to turn on your clipping. This will show in bright blue on your image for where your darks are, and will allow you to see how you are adjusting your image as you move the sliders.

*End Tutorial*