TECHNIQUE: Better exposure with Layer Masks

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TECHNIQUE: Better exposure with Layer Masks
By Shelleyrae Cusbert 2008
Jun 26, 2008, 00:27

Layer Masks: Exposure Correction

This tutorial demonstrates how the use of a Layer mask and gradient can assist in correcting exposure problems in a photo. The type of photo particularly suited to this method is one where up to a half of the image is correctly exposed and the other half is shadowed.
In this example, the sun that is low in the sky at right has lit the left side of the scene but thrown the right into deep shadow, hiding detail and color.

Open the photo to your workspace. Make a duplicate (Image> Duplicate) and close the original.

Use CTRL+J to create a duplicate and hide the bottom photo layer
To add a mask to the photo, find and click the mask icon at the bottom of the layers palette. This adds a white rectangle to the layer.

Ensure your foreground color is black and the background white in the color well. (Press D on your keyboard) and then select the Gradient tool from the toolbox palette.

On the Options Toolbar, select the gradient that runs from black to transparent. Ensure that Linear Gradient is selected, and Transparency is checked.

Click on the white layer mask in the layers palette. With the gradient tool, draw a line that starts from the edge of the photo and extends slightly into to the area that you wish to edit.
The gradient shows on the layer mask. If your selection is not what you wanted, simply redo the gradient line.

Turn the layer visibility on for the Background layer

Click on the photo (not the layer mask) of the duplicate.
Go to Image> Adjustments> Curves

To lighten the areas that are shadowed, push the lower right of the curve up slowly. Manipulate the curve to regain detail. Be careful to not blow out any light areas or distort colors. Also ensure that a seam does not appear where the two photos merge.

In this instance I have lost some color in the sky at right. To correct this, we can paint directly on the mask to hide the changes.
Ensure that the color well is set to the default with black as the foreground. Choose a round brush at a size to suit. Click on the layer mask and then brush over the area of the sky. You will see on the mask that the area blackens as you brush over it to show transparency.
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Apply any further edits the image with the layer mask. You may find you need to make adjustments to contrast and saturation so help it better match the other half.
When you are satisfied with your edits, merge the two layers.
Make any overall changes to the image and then save.
After /Before
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