As you use the Adjustment Panel you'll find that there is some overlap among some of the controls in Aperture. In the Exposure brick there are options to set the overall exposure, as well as the Black point, Recovery and Brightness. A little further down in the panel is the Levels brick where you can also set a black and white point and modify overall brightness. So how do you know which to use?

The more familiar you get with the controls, the more aware you’ll become of the subtle differences. In my workflow I begin by setting the Exposure slider to determine the overall exposure for the image. I try to balance minimizing clipping in the highlights and then the shadows while keeping the majority of the mid range tonalities close to where I’ll want them. Then I use the Recovery slider if I have some highlight clipping to try to reduce or remove the clipping. The Recovery slider is accessing information that was captured by the sensor but is not presently used in the image. It’s different than the Highlight slider which is modifying the lightest 25% of the tones that are visible within the file.

If the image seems overall too dark or too light, I’ll use the Brightness slider.

Deciding to tweak the Black Point slider or set the black point by using Levels is a very image specific choice. Using the Black Point slider affects the black point but has less impact on the rest of the tonalities. If you move the farthest left slider in Levels over to where the data begins in the histogram, more of the tonalities will be affected. That means that when you use the Black Point slider you can see some definitive blacks but you won’t make a lot of the darker tones still darker. However if you set the black point by moving the slider in Levels to where the data begins,more tones will get darker. (Tip: Hold down the Command key while pulling the slider to see a clipping preview and to accurately set the black or white point in Levels or the Exposure brick.)

I opt to use the quarter tone controls in Levels and often bring them inwards a little to increase the midtone contrast. At times I’ll modify the placement of the quarter tone sliders so that they’re closer to the extremes or to the middle. That way I can control the range of tonalities that are becoming more contrasty. (This is similar to changing where you make the points for the S curve in Curves.) To change which tonalities are affected by the quarter tone sliders, hold down the Option key while dragging the slider. I find that I have more control over the midtone contrast that way rather than using the Mid Contrast slider that’s in the Highlight/Shadow brick.

If you have any tips for making tonal adjustments, feel free to post them.