What is the Curve Tool?

The curve tool is a vital tool in photography. It allows you to make exposure adjustments and apply color grading during post-editing.

The curve tool is available in various software applications. In this article, we will use Adobe Lightroom and Adobe Camera Raw as references, but you can apply the same principles in many other programs.

💡 Tip

If you are using Lightroom mobile, the curve tool is located inside the "Light" section.

How to Read the Curve Graph

Before diving into the practical aspects, it's crucial to understand the components of the Curve Graph.

The Vertical Axis

The Vertical Axis is the "Result" Axis (output), where you determine the desired outcome. For example, lifting an anchor point brightens the targeted area, while lowering it darkens the area.

The Horizontal Axis

The Horizontal Axis is the "Target" Axis (input), where you select the tonal values you want to target and adjust.

The tonal values progress from left to right: Blacks, Shadows, Midtones, Highlights, and Whites.

If you add an anchor point to shadows, you will adjust the shadows. Adding an anchor point to highlights allows you to control the highlights.

What Is The Point Curve

The point curve is one of the most frequently used and powerful curves. You can add multiple anchor points and customize the brightness and contrast of your photos according to your preferences. 

How to Use the Point Curve

Suppose you have a dark photo that you want to brighten. To achieve this, it's a good idea to lift the shadows:

1. Click and add an anchor point to the diagonal line corresponding to the shadows (left side of the Horizontal Axis).
2. Move the anchor point upwards. Since you are targeting the shadows and moving the anchor point upward, the shadows will become brighter.  
3. Add extra anchor points if necessary.

You can apply the same logic in reverse. For example, if your photo is too bright, you can add an anchor point to the area of your photo that's too bright and lower the anchor point. You can also add more anchor points and combine these methods.

💡Tip

An easy way to enhance the contrast in your photos using the curve tool is by creating an "S Curve" with two anchor points.

1. Place the first anchor point in the shadows and decrease their intensity.
2. Position the second anchor point in the highlights and raise their brightness slightly.

What Is The Parametric Curve

The parametric curve is similar to the point curve, but the key difference is that it won't allow for large adjustments. Your curve will always be controlled. This is ideal for making small adjustments or for beginners.

How To Use the Parametric Curve

1. Choose the Parametric Curve from the curve panel.
2. Adjust the areas you want to target by clicking and dragging the diagonal line, or by using the sliders for Highlights, Lights, Darks and Shadows located under the graph.
3. If necessary, fine-tune your targeted areas by utilizing the button-sliders located under the graph.

Color Grading With The Curve Tool

The Curve Tool is not limited to exposure adjustments; you can also use it for color grading. The principles of the Horizontal and Vertical axes remain the same.

There are three Point Curves for color grading:

1. The Red Point Curve, which controls the red channel.
2. The Green Point Curve, which controls the green channel.
3. The Blue Point Curve, which controls the blue channel.

The Red Channel Point Curve Tool

The Red Point Curve allows you to adjust the red color in your photo. Understanding color theory is crucial here. Adding red will make your photo appear Redder, while reducing red will make your photo appear more Cyan since Cyan is the opposite of Red on the color spectrum.

Moving your anchor points up on the Vertical Axis adds Red color, while moving them down adds Cyan.

The Green Channel Point Curve Tool

In the Green Point Curve, raise your anchor points on the Vertical Axis, and you will add Green to your photo. If you drag your anchor point down, you will add the opposite color of green, which is Magenta. (Magenta it's often described as a pinkish-purple color)

Moving up adds Green, while moving down adds Magenta.

The Blue Channel Point Curve Tool

The Blue Point Curve works the same way as the other two. When you lift your anchor points up, you add Blue to your photo; when you drag your anchor points down, you add the opposite color, which is Yellow.

Up Blue, down Yellow. 

How To Use Point Curves For Color Grading

Apply the same principles as the regular Point Curve, but keep in mind the element of color. Add your anchor points somewhere on the diagonal line and drag it up or down.

You can make it really complex by using all three color point curves and adding multiple anchor points, or you can keep it simple by using only one color point curve with just one anchor point.

Add anchor points only where you want changes to appear.

What Is The Targeted Adjustment Tool

Instead of manually adding anchor points, you can use the Targeted Adjustment Tool for a more precise adjustment. You can find this tool in both the Point Curves and Parametric Curve.

 

How to Use the Targeted Adjustment Tool

1. Click on the Targeted Adjustment Tool.
2. Choose the curve tool you want to adjust. You can select it from either the curve tool panel or the floating bar.
3. Click on the photo to select the area you want to adjust.
4. Adjust the anchor point to your preference.
5. Add extra anchor points if necessary.

💡Tip

You can target the HSL Sliders with the Targeted Adjustment Tool as well, but this is for another time.

In conclusion

Curves are powerful tools in photography editing, accessible to both beginners and professionals. They allow you to fine-tune exposure and colors in your photos, either together or separately. Remember that the complexity of the curves is flexible, so use only the necessary tools for your editing needs.

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