ADJUSTMENT LAYERS

Clive R. Haynes FRPS

Why do we need them? Consider this: usually, when an adjustment is made to an image, the pixels are irrevocably altered in some way.

Prove this to yourself by opening an image, then via the Image > Adjust > Brightness/Contrast route, radically alter the brightness and the contrast and note the position of the two slider controls. Click OK and return to the image.

Open the Brightness/Contrast adjustment again. Note the position of the two 'sliders' - they've reset to zero! This, then, is the new starting point. Now, try by adjusting the sliders to restore the image to how it was before - hmmm, not possible I think you'll agree.

How splendid it would be if we could return to the point at which we left the sliders and alter/restore from that point. Photoshop allows this - via an Adjustment Layer.

Making an Adjustment Layer will give you complete control over the following:

Levels

Curves

Brightness/Contrast

Color Balance

Hue/Saturation

Selective Color

Channel Mixer

Invert

Threshold

Posterize

Creating an Adjustment Layer.

At the base of the Layers palette, click on the half black / half white circle icon

From the list that appears, choose (in this instance) Brightness/Contrast.

The Adjustment Layer appears above the Layer you had activated.

Note: as the Adjustment Layer is above the lower layer(s) it will affect all Layers beneath.

Now, to prove the advantage of the Adjustment Layer, follow the experiment below.

Radically alter the position of the two (Brightness/Contrast) sliders.

Click OK.

Return to the Adjustment Layer by double clicking on it or via Layer > Adjustment Options - this time you'll see that the sliders are where you left them set. They are available to be adjusted again. This wonderful facility exists for all the 'Types' named in the Adjustment Layer dialogue box drop-down list.

You can have several different Adjustment Layers running, all controlling different settings if you wish.

Having created one or more Adjustment Layer, it may not be convenient for it to cause changes to all the layers beneath. Photoshop will allow you to bind one or more Adjustment Layers to the required image layer by 'clipping' the Adjustment Layer to it.

This is how you do it.

Create your Adjustment Layer and click OK.

Whilst holding down the Alt key, move the cursor over the junction between the two Layers ('Adjustment' Layer above and 'image' layer below). As you slowly cross the dividing line, the cursor will change from an arrow shape to that of a tiny black/white eclipse symbol, when you see this, click (mouse) or press (Wacom pen) on the line and the two adjustment layer thumbnails will displace to the right. AND a downward arrow will appear upon the layer, indicating that it is 'clipped' (associated) to the layer beneath.

Left: Clipping Group - the upper layer is 'clipped' to the lower.

The two Layers now form a 'Clipping Group' and adjustments made will only affect the image layer to which it is 'clipped'.

To 'unclip' the two layers, repeat the above procedure and they detach from one another.

You can introduce more Adjustment Layers into the group and you can create other Clipping Groups in the stack of Layers.

Just in case you're concerned, all Layer information is stored when you 'Save' - so you can return to the point you've been working on when next you 'Open' the image.

Each Adjustment Layer can be labelled to identify it if you so wish by the Layer Options route.

Notice that the Adjustment Layer has a small 'mask icon' to its left (a circle within a grey square set between the large rectangle and the eye icon) - more about this feature later.

Should you wish to adjust a specific area within the image, you can do this by making a 'selection' in one of the usual ways ('inverse' it if you need) then creating an Adjustment Layer. The area in the Adjustment Layer window thumbnail will show the part you've selected - any adjustments you now make will only occur in that area. However, by painting on the Adjustment Layer with black or white paint (notice the mask icon - which is indicative of this useful masking function) will add to and subtract from the original area - experiment and see. More about masking soon.