Today’s Question: I’m finally starting to learn to use the Curves adjustment in Photoshop. Previously I had done my basic tonal adjustments with Levels. Once I am comfortable with Curves, is there any need to use Levels at all?
Tim’s Quick Answer: Once you’re comfortable using the Curves adjustment in Photoshop there’s no need to use the Levels adjustment at all.
More Detail: The Curves adjustment can be used to apply all the adjustments that are possible with Levels, and more. Therefore, if you’re comfortable using Curves there’s no benefit to using the Levels adjustment.
The Levels adjustment is used primarily for setting the black point and the white point, as well as for applying a middle tone adjustment. In Curves there are sliders below the curve area for the black point and white point, which operate in exactly the same way as the same adjustments in Levels. The effect of the middle tone slider in Levels can be reproduced by adding an anchor point at the center of the curve line and dragging it directly upward or downward.
In this way you can think of the Levels and Curves adjustments as providing the exact same adjustment options. The difference is that the Curves adjustment offers considerably more power, with the ability to add additional anchor points to manipulate the shape of the curve, and therefore focus adjustments in specific areas of the image based on the underlying tonal or color values.
For example, you can brighten the shadows and darken the highlights by adding anchor points on the curve in the appropriate positions. You can even apply a color balance adjustment differently for the highlights versus shadows, for example, by using additional anchor points on the curve for an individual color channel rather than working with the composite RGB channel that only provides tonal adjustments.