Photoshop: gradation curve - simply explained

The gradation curve in Photoshop can be used to edit points in the entire tonal range of a graphic. This offers a variety of options for changing the color channels and thus reworking the images. The following practical tip explains how to use the gradation curve.

Photoshop: Open the gradation curve

Before you can edit the gradation curve, you must first open it. Photoshop offers two different ways to do this:

1. The easier way is to open the curve using the key combination "Ctrl + M".
2. Alternatively, you can open the gradation curve by first selecting the menu item "Image", then "Corrections" and finally "Gradation curves".

Explanation of the gradation curve in Photoshop

Gradation curves can process any point in the tonal range between 0 and 255. Treble, bass and midtones can be edited independently. The editing does not only refer to the entire image. You can also use e.g. B. only edited the heights of the color channel red and leave the remaining color channels as they are.

• If the gradation curve is open, you will see a diagonal gradient. It shows the gradient of the tonal values ​​in the graphic from dark (left / bottom) to light (right / top).
• You can choose from various presets using the "Presets" drop-down menu. For example, the "Color Negative" default reverses all colors in the graphic.
• You can select the different color channels using the "Channel" drop-down menu. You can choose between red, green, blue and all three channels together.
• The curved line in the left area of ​​the gradation curve window allows you to add points on the diagonal. You can move these points and thus change the tonal values ​​of the graphic. With the help of the pen you can draw the course of the gradient freely.
• In the right area of ​​the window you can edit the specifications, such as the grid of the curve, activate the preview and make an automatic correction of the curve.

Easy image correction using the gradation curve

There is no general way to correct the image with the gradation curve. After all, the correction requests vary from image to image and are also subject to your own feelings. The most common correction, however, is post-processing of over- and under-exposed photos. To correct the overexposed sample image, proceed as follows.

1. On the left side you can see the overexposed original. This is now to be made darker. Since the picture is largely composed of midtones, these must be darkened. The highs and lows remain at their initial values.
2. To do this, pull the middle of the gradient, which represents the midtones, down a little. The preview in the gradation curve window allows you to check your corrections in real time before you confirm them.
3. If you would now like to make the low tones lighter, you would have to pull the origin of the gradient upwards.
4. To make the heights darker again, you would pull the end of the gradient down.

Change tonal values ​​based on the original graphic

Even more precise corrections are possible if you edit the gradation curve based on the original graphic. To do this, open the gradation curve again.

1. Three pipettes are displayed in the lower part of the gradation curve dialog window. These represent the highs, lows and midtones.
2. To take the color values ​​from the original graphic, select the pipettes one after the other and take the corresponding color from the graphic.