94. Create an Adjustment Layer
Before You Begin
91 About Layers and the Layers Palette
92 Create a New Image Layer
100 Mask an Adjustment or Fill Layer
If you want to make adjustments to the color, contrast, brightness, and saturation of the layers in your image, you can add an adjustment layer. An adjustment layer changes the appearance of the layers below it in the layer stack without affecting the actual contents of those layers. This enables you to try out various adjustments without making any permanent changes to the image layer(s). If you don't like the result, you can open that adjustment dialog box again and make other changes, which is the same as if you had clicked Undo and had started over. However, in this case, you can change your mind at any time, even way down the editing process! You can also remove the adjustment layer and its effects completely.
Adjustment layer A special layer that allows you to make a specific color or contrast adjustment to the layers underneath it.
There are several types of adjustment layers you can create:
Levels. Allows you to adjust the highlight, midtone, and shadow values for each color channel or the entire tonal range. You can also remove a color cast using Levels. See 138 Improve a Dull, Flat Photo.
Because its effects are easy to change or remove, an adjustment layer is always preferable to applying that same adjustment directly to a layer. In addition, using the adjustment mask, you can easily limit the adjustment to particular portions of the layers below, and even change your mind on which portions you want affected, any time you want.
Brightness/Contrast. Allows you to decrease or increase the general amount of brightness and contrast for all pixels on the affected layers. See 137 Improve Brightness and Contrast.
Hue/Saturation. Allows you to adjust the hue, saturation, and lightness of all pixels on the affected layers. See 146 Adjust Hue, Saturation, and Lightness Manually.
Gradient Map. Applies the colors in the gradient you select to the pixels in the affected layers, based on their brightness value. See 71 Make Areas of an Image Easier to Select.
Photo Filter. Allows you to apply an effect that simulates the use of a particular photo filter to the affected layers. For example, if you want your image to have a sepia appearance, apply the Sepia photo filter.
Invert. Changes the pixels on the affected layers so they are reversed in color and tone. See 71 Make Areas of an Image Easier to Select.
Threshold. Allows you to convert the pixels in the affected layers to either black or white. Light areas are converted to white and dark areas are converted to black, depending on the threshold you select. See 71 Make Areas of a Photo Easier to Select.
Posterize. Allows you to control the number of tones in the affected layers by specifying the number of brightness levels you want. The brightness of each pixel is then adjusted to fit within one of these tonal levels. See 71 Make Areas of a Photo Easier to Select.
Select Layer Position
Open an image in the Editor in Standard Edit mode and save it in Photoshop (*.psd) format. In the Layers palette, select the lowest layer you want to be affected by the adjustment layer. The adjustment layer will appear in the Layers palette above the layer you select and will affect all layers below.
To create an adjustment layer that automatically adjusts only the area within a selection (and not the entire layer), make that selection first in step 1.
Select Adjustment Layer Type
Choose Layer, New Adjustment Layer from the menu bar and then select the type of adjustment you want from the menu that appears. Regardless of the type of adjustment layer you selected, the New Layer dialog box opens to request basic information about the new layer.
You can also create an adjustment layer by pressing Alt, clicking the Create Adjustment Layer button on the Layers palette and selecting the appropriate adjustment layer type. (The Alt button causes the New Layer dialog box to display, so you can change its settings as desired; if you don't press Alt, the layer is added using the default values.)
Specify Layer Settings
On the New Layer dialog box, in the Name field, specify the desired name for the layer. Adjust the Opacity and blend Mode if desired. Click OK.
If you enable the Group with Previous option in the New Layer dialog box, you'll create a clipping mask and your chosen adjustment will apply to only the opaque pixels in the layer directly below (and it will not affect other layers below the next lowest layer). You can limit the adjustment even within this opaque pixel area, through its mask. See 163 Mask an Image Layer for more on clipping masks. See 100 Mask an Adjustment or Fill Layer to learn how to change the adjustment layer mask.
Specify Adjustment Layer Settings
Depending on the type of adjustment layer you create, a different dialog box displays. For example, if you select the Levels adjustment layer type, the Levels dialog box displays. Make the appropriate selections for the adjustment layer you want to create. For example, on the Photo Filter dialog box, select the default filter or color you want to use to filter the layers. Then specify the density level for the filter.
When you have specified the appropriate settings for the type of adjustment you want to make, click the OK button to apply the adjustment filter.
The adjustment layer you create affects only the layers below it in the layers stack (unless you create a clipping mask). If you don't want a layer affected by the adjustment layer, you can move that layer above the adjustment layer by dragging it in the Layers palette.
If you want to make modifications to an adjustment layer later, click the adjustment thumbnail on the Layers palette. The corresponding dialog box displays. For example, if I clicked the adjustment thumbnail for my Photo Filter adjustment layer, the Photo Filter dialog box would display showing the current settings for the adjustment. Make the desired changes and click OK.
View the Result
Unless you created a clipping mask, the adjustment you choose is applied to all layers below the adjustment layer. You will notice that in the Layers palette there are two icons for the layer. The first icon shows the type of adjustment that was added. The second icon shows the mask. It's white where the fill shows through to other layers, and black where the fill is blocked. Unless you made a selection in step 1, you'll notice that the mask is initially white, meaning that the adjustment completely shows through at the moment, affecting all data on the layer below. You'll learn how to edit the mask to block the effects of the adjustment so that it only affects portions of the layers below in 100 Mask an Adjustment or Fill Layer.
When you're satisfied with the image, save the PSD file. Then merge the layers together and resave the result in JPEG or TIFF format, leaving your PSD image unflattened so that you can return at a later time and make different adjustments if you want. In this example, I created a Photo Filter adjustment layer. I then applied the Sepia filter and set the Density level to 100. Although this alteration is difficult to appreciate in the black-and-white images shown here, this adjustment made the photo look like it was taken with an old camera, changing all the colors in the image to various shades of brown.