Curves

A second way to carry out color corrections is by means of the “Curves” option.
In the previous lesson we saw how we can make color corrections for the three points highlights, midtones and shadows using “Levels”.

When we use curves, we can customize each of the 256 gray levels.  In this example I’ll show you how to adjust the brightness and contrast through curves.

As always, I start by making a copy of the original photo.
Open the window “Adjustments” and click the “Curves”. 

This opens the “Curves” panel.

Let us first see what we have here.  What is most striking is the diagonal line (1) in the graph that runs from the lower left to upper right.

The point in the upper right corner represents the lightest color, the point in the lower left corner represents the darkest color. In between are various shades of gray.

And at bottom and side of the chart, we have two bars, which are provided with a gradient from black to white (2).

The image under the graph represents the display in the picture at that time.

When we work with curves, old view is replaced with new view.
This new view is seen in the vertical bar.

As an example I want the midtones of the image lighter. How do I proceed?

The mid-range are located in the middle of the graph. So I click in the middle of the chart and drag the mouse pointer up.

You can see that the horizontal axis is moving upwards (2) and the new midrange is lighter.

The later can be seen at the intersection of the horizontal axis with the vertical bar (3).

You will find a number of different preset curves in the “Curves” (4).

You know that you should try this and see how the diagonal line is adjusted to the option you have chosen.
The first thing we do is to select the “Show Clipping for black and white points” option so that it is activated.  Just click the downward pointing arrow in the title bar of the “Adjustments” pane and click this option.

Then we set the light colors.

Click and drag the white triangle above the bottom right of the graph to the left (1). Once you see the white color appear in the picture, release the mouse button.

We do the same for the dark colors.  Click and drag the black triangle below the graph from left to right (2). Once you see the black color appear in the picture, release the mouse button.

And finally we fit the curves on the “Curves” panel.

For this, select the “Edit Curve” button in the “Adjustments” panel and click and drag the picture up or down. Move the mouse pointer up, the picture gets lighter, move it down, then the picture gets darker.

As you click and drag the cursor you see the curve move and you will see an example in the picture.

This places a point in the curve at the position of the cursor in the picture (4).

If you want to make a particular place in your picture darker, you can still drag this point to the right. If you want it lighter, slide your point to the right.

If you want multiple reference points on the diagonal line in the graph, you can do this with the “Curve editing” button or by clicking on the diagonal line. When you choose the later, you do not know, of course, what position it represents in the picture.

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