Adjustment layers are among the most useful editing functions, partly because they enable you to edit non-destructively but also because you can use the Layers function to select part of an image and work on it without affecting the remainder of the image. The best way to visualise layers is as transparent overlays upon which specific effects are applied.
Think of Layers as transparent overlays. The screen grab on the left shows the Layers palette containing two layers, both of which are visible. The active layer is indicated with a blue fill. This layer has been darkened to accentuate the sky. Clicking on the eye icon in the lower layer switches the visibility off, showing the upper adjustment layer. Note how the Opacity slider has been used to reduce the strength of this adjustment.
When you open an image file it becomes the Background layer. To open a new adjustment layer, select Layer from the top menu bar and click on either Layer or New Adjustment Layer in the dropdown menu.
New Adjustment Layer is used when you know precisely which action you will carry out. It saves time by opening the appropriate dialog box for the action selected. Clicking on Layer means you must select the action separately.
Two ways to create an adjustment layer from the dropdown menu in the menu bar. Note the range of specific actions provided in the New Adjustment Layer dropdown menu.
The Layers palette helps you to keep track of the layer you are working on and control the visibility of other layers in the stack. It also provides a number of basic controls.
The Layers palette is circled in red. There are three layers in the stack: the background, Layer 1, which is a copy of the background, and Layer 2, which has been produced by selecting the two large rocks in the foreground of the scene, which were a little too dark. This layer is shaded in blue to indicate it is the ‘active’ layer.
A blue background shows the layer that is being worked upon. Clicking on the eye icon switches the visibility of the selected layer on and off. In the illustration on page 23, the brightness and contrast of the selected rocks have been adjusted by clicking on Image>Adjustments> Brightness/ Contrast and moving the sliders to the right. The rest of the image is unchanged since it is not part of the active layer.
This illustration shows how easy it is to work on individual layers. After adjusting the sky in Layer 1 to make it a little darker and less contrasty to bring out the clouds, we used the eraser tool with a very large, soft brush to ‘remove’ the dark parts of the picture and keep the normal tones of the foreground. The previously-adjusted rocks in Layer 2 can be seen sitting above the other layers when the visibility of the Background layer is switched off.
There are two other important sections in the Layers palette. The Opacity slider on the right lets you adjust the transparency of the layer you’re working on between 100% (totally opaque) and 0% (totally transparent). Left of it is a dropdown menu containing the various blending modes. The default Blending mode is Normal and most photographers will leave it unchanged, at least initially.
Moving, stacking locking and deleting layers
It’s easy to change the order of layers in a stack; you simply drag the selected layer (or group of layers) up or down in the Layers panel. Release the mouse button when the highlighted line appears where you want to place the layer or group. You can also reverse the order of selected layers, by selecting Layer > Arrange > Reverse. These options appear dimmed if you don’t have at least two layers selected.
Clicking on the Lock icon (circled) will lock the layers in a selected group.
You can lock layers fully or partially to protect their contents. Select the layer or group of layers and click on the Lock icon. Each layer in a locked group will display a dimmed lock icon. To partially lock a layer, select the layer then click one or more lock options in the Layers panel. Locking transparent pixels confines editing to the opaque portions of the layer. Locking image pixels prevents them from being changed with the painting tools. Locking position prevents the layer’s pixels from being moved.
You can also apply lock options to selected layers or a group by selecting the layers and choosing Lock Layers or Lock All Layers In Group from the Layers menu or the Layers panel menu. Deleting a layer has no effect on other layers ““ or the background image.
Layers are great for keeping track of editing adjustments because you can make each change on a different layer. It’s easy to switch the visibility of selected layers on and off and delete selected layers if you’re not happy with the results.
‘Flattening’ the image (Layer > Flatten Image) combines all the layers into a single image. Unless the image has been saved at this point, most editors let you step backwards and ‘un-flatten’ them if you want to make subsequent changes to individual layers.
Some image editors allow you to save images with layers in place and re-open them for further editing. This usually produces very large files so most editors require the image to be flattened before it can be saved.
Layer Blending modes
Choosing a layer Blending mode adjusts the way the pixels in the selected layer interact with those in the layer below. The default Blending mode is Normal and most photographers will leave it unchanged, at least initially.
At 100% Opacity the default Normal mode simply shows the image on top of the layer stack. Dragging the opacity down to 50% when the top layer is selected allows the lower layer to show through.
Layer blending was used to bring out details in the sky in the top image. A Black & White layer was created and sepia toned and then the Screen blending mode was selected and the Opacity slider was moved to 50%.
The Blending modes menu is divided into five sections covering the following adjustments: darkening, brightening, contrast, effects and colour. It’s fun to explore them and see the effects they have, even though you may not want to use any of them. The main advantage of these modes is that it is very easy to control how much of the effect is applied with the opacity slider, which provides a high degree of fine-tuning.
Two of the more useful blending modes for beginners are the Screen and Multiply modes, which lighten and darken the layer respectively. Other potentially useful modes are the Overlay and Soft Light modes, which can be used for controlling contrast.
An example of how the Blending modes can be used to add subtle (and not so subtle) effects to images. The top image shows the original shot, while the bottom shows the image after adjustment with the Vivid Light blending mode, which increases saturation while maintaining the original brightness levels. Note the positions of the Opacity and Fill sliders, which are used to fine-tune the effect.
Excerpt from Photo Editing Pocket Guide