Adjustment Layers

Clive R. Haynes FRPS

Adjustment Layers
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. Good news!
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.

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

Saving
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.

Name the Layer
Each Adjustment Layer can be given a name to identify it just like naming any other Layer.

The Adjustment Layer 'Mask' Facility
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) - this is the 'Mask' icon and it means that the changes that you have made on the Adjustment Layer can be selectively changed - just like a 'Layer Mask', that is to say with the Adjustment Layer active, 'painting' on the image with black or white will add to and subtract from the adjustment you have made - experiment and see.
By using this feature, you can very accurately alter the intensity (by brush pressure) of the adjustment you have created and the extent to which it affects all or part of the image. This is really very useful.

Using the Layer Mask within the Adjustment Layer
When the Adjustment Layer is activated (the layer goes blue). Painting with black will paint-out/undo the Layer Mask effect and swapping white (as the foreground 'paint' colour) will restore it. Of course different brush pressures and opacities will cause the effect of 'painting' to be greater or lesser.
Note: If you have created a 'mask' for the Layer via a 'selection' in the first place (as described below), then painting with black / white can extend or erase the extent of the area initially selected - this is really useful! Try it.

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 as mentioned above