Photoshop Curves
Darken Corners

Sometimes darkening the corners of an image helps keep the viewer focused on the image.  I prefer to use Levels to accomplish this.  But it can also be accomplished using Curves.  This topic shows how to use the Curves adjustment to perform this task.

Figure 1. Curves Dialog Box

 

Figure 2.  Options bar

 

Figure 3.  Gradient Editor

 

Figure 4.  This is what the layer mask should look like

 

Before

After

Figure 5.  Mouse over the labels to see the effect.

To darken image corners...

1. Ctrl + zero (Command + zero) to fit the image on screen.
2. Type the letter f until the image is in full screen mode with menu bar.  This mode puts a gray background around the image.
3. Create a Curves adjustment layer by clicking Layer > New Adjustment Layer > Curves.  Or, by clicking the Create new adjustment layer icon at the bottom of the Layers panel.
4. Drag the upper right anchor on the curve down until the image darkens.  See Figure 1.
5. Click OK to close the Curves dialog box.
6. Change the blending mode to Luminosity.  This will prevent color from being affected.
7. Make the Gradient tool the active tool.  It shares the same spot as the Paint Bucket tool in the Tools panel.
8. Type the letter d to set the foreground and background colors to the default black and white .
9. Type the letter x until black is the foreground color.
10. Now we will draw a radial gradient in the layer mask of the Curves adjustment layer.  This will confine the darkening to the corners.
11. In the Options bar, click the radial gradient icon .  See Figure 2.
12. In the Options bar, click the gradient drop down box to open the Gradient Editor dialog box.  See Figure 2 for the area to click.
13. In the Gradient Editor dialog box, click the Foreground to Background preset.  See the top of Figure 3.
14. Then drag the left most Color Stop handle to the right until Location says about 60%.  This will cause most of the gradient to be black and help confine the darkening to the corners.  For now, let the Color Midpoint  handle move on its own.  When you drag the color stop, the name of the gradient will change to Custom.
15. Click OK to close the Gradient Editor dialog box.
16. Click near the middle of the image and drag the cursor till it is just outside one of the corners and then release the mouse.  This will cause the radial gradient to be drawn in the layer mask.  The layer mask should look something like Figure 4.
    1. Tell me how to find the middle of my image
       1. Click Image > Image Size
       2. Note the width and height of the image in pixels.
       3. Click Cancel to close the Image Size dialog box.
       4. Click View > New Guide
       5. Make sure Vertical is checked.
       6. In the Position text box, type half the width of the image.  Follow the value by px. For example, if the image width is 504 pixels, type 252px in the text box.
       7. Click OK.  A vertical ruler guide will be created.
       8. Click View > New Guide again.
       9. Make sure Horizontal is checked.
       10. In the Position text box, type half the height of the image.  Follow the value by px. For example, if the image height is 311 pixels, type either 155px or 156px in the text box.
       11. Click OK.  A horizontal ruler guide will be created.
       12. Where the two ruler guides intersect, is the middle of the image.
17. The edges of the image should now be darkened.  Mouse over Figure 5 to see before and after versions.
18. The gradient can be redraw until the desired areas are affected.  If necessary, you can open the Gradient Editor dialog box and move the left Color Stop or the Color Midpoint handle to adjust how much of the gradient is solid black.  If the Color Midpoint handle is not visible when you open the Gradient Editor dialog box, click the left Color Stop handle once.
19. To adjust how much the corners are darkened, open the Curves dialog box and move the adjustment point to make the corners more or less dark.

points to remember

• Make sure the Curves adjustment layer is the active layer throughout the entire process.
• The layer mask controls what is darkened.
• The Curves adjustment controls how much it is darkened.
• When actually drawing the gradient, if you drag too far outside the image, then the layer mask will be completely black and will negate all effects.
• When drawing the gradient, drag it to a corner and not to the middle of an edge.
• When drawing the gradient, if when you release the mouse you see the black and white gradient in the document window, then the gradient was drawn on the image and not in the layer mask.  Undo the gradient, click the layer mask thumbnail to select it and redraw the gradient.