Working with Layers

Digital Imaging

by Hans Weichselbaum

Working with layers

Working with Layers

Working with Layers

It was in 1994 when Adobe introduced layers into Photoshop 3.0 – and a whole new world of artistic freedom and design possibilities has opened up. Today, 14 years later, it is difficult to imagine working in Photoshop without layers.

The concept is simple, so simple indeed that it is covered in any beginner’s course. It is like having a stack of papers, each sheet with its own image. We look at the top sheet, but we can make individual layers invisible, change the order or reduce the opacity, making the layer more or less transparent.

The great thing about layers is that you can have different versions of an image in one and the same file. For example, you can have the original image at the bottom of the pile and the edited versions in various stages of progress on top. You can always go back to a previous version with the click of a button. The problem is that the file size quickly mushrooms out of control. A file with four layers will roughly be four times the size of the original single-layered file.

A very elegant form of editing images is to work with Adjustment Layers. They hardly add to the file size and allow you to come back to your editing steps and change them any time without affecting the original image pixels.

And there is more you can do with layers. The Blending modes give you control over the way the individual layers interact with each other. This is one of the more advanced controls, often puzzling even to the experienced Photoshop user. But we will leave that for a follow-up article. Let’s first have a look at the Layer Palette.

The Layer Palette Image 1 shows you an example with three image layers and two adjustment layers. At the bottom of the pile we see the ‘Background’ layer. This is the default layer, if you have only one image layer.

The little padlock on the right lets you know that the layer is locked. If you go to the Edit menu you will see that the Stroke and Transform commands are greyed out. If you double-click on the layer in the Layer Palette you get the option of naming the layer, or simply accept the ‘Layer 0’ default and press OK. Now you can frame your image (with the Stroke command) or distort it under Transform.

Make a copy of the current layer by pulling it with the mouse over the ‘Create a new layer’ icon at the bottom of the palette. You now have an identical image layer sitting on top of the original Background layer.

Another important control is the eyeball at the left of each layer. By clicking on this eyeball you can switch the visibility of the layer on and off. If the visibility of a particular layer is switched off, you get the image of the layer immediately underneath.

After making a duplicate layer you can do some editing, for example get rid of a colour cast with the Curves command, which we discussed last time. Now you can use the eyeball to switch between the before and after version. A good way of doing colour adjustments is to exaggerate the correction on the new layer and then reduce the Opacity to a value of less than 100%. This will let the layer underneath blend into the upper layer.

Once you have two or more layers you can save your image and retrieve it at any later stage with the layers intact. If you want to get rid of the individual layers, go to the Layer menu and choose ‘Flatten Image’. In earlier versions of Photoshop only PSD files were allowed to have layers, however, later versions also allow you to save layered TIFF files (but not JPEG). But keep in mind that no other programme can read those layered TIFF files! For good housekeeping I recommend saving layered files in PSD and flattened files as TIFFs.


Adjustment Layers (image 2 below)

Creating a new layer every time you do some editing is not a good idea. As we saw, every layer adds a lot to the image size and the layer palette would soon become very cluttered. A much more elegant way is to work with Adjustment layers: here we only save the original pixel data, plus all the instructions on how to get to the final image.

You can imagine an adjustment layer as sitting on top of the image and acting like a filter. You see the image as if the changes have been applied. But they haven’t been applied permanently. You can go back anytime and undo the changes, or finetune the settings. We have been told to keep the number of editing steps to a minimum, because every time we do something to our image, we throw data away and the gaps in the histogram just keep growing. With adjustment layers we can apply as many incremental changes as we like. We can have a whole bunch of adjustment layers – they will act as if only one change has been applied to the image data.

To create a new adjustment layer, simply click the New Adjustment Layer button at the bottom of the Layers palette. Up comes a whole list of options, including the familiar Levels, Curves, Hue/Saturation etc.

The adjustment layer can also be switched on and off by clicking on the eyeball of the layer. We can go back to our settings anytime by double-clicking on the layer thumbnail and change the parameters, without the penalty of applying the changes permanently to the image pixels.

Another way of finetuning the settings is to exaggerate the effect you want to achieve and then reduce the opacity of the layer.

You might have noticed the white rectangle on the Layer Palette that comes with every new adjustment layer. This is a Layer Mask. The white colour means that the changes are applied to the whole image. In the followup article we will look at how to apply changes selectively to parts of the image and we will touch on the mysterious Blending modes.