The Photoshop file format has a layered structure. Simply put: each document is composed of many image layers on top of each other. This enables each part of the final ‘composite’ image to be changed independently of the others. The composite image in the document window is a flattened view of all of these separate layers.
- 1 Bottom of palette
- 2 Top of palette
- 3 Layers
- 4 Layer syntax
- 5 What can go wrong?
- 6 Layer Palette keystrokes
Bottom of palette
The bottom of the Layers Pallet contain a set of icons that are used for creating items within the layer stack.
Two layers linked will move unison. Useful for web design, interface design etc. To a digital painter this is not really useful.
B: Layer effects
Activates layer effects from a menu. These are pre-made effects such as: drop shadow, inner glow, emboss etc. These are useful for web design, interface design etc. In this course this is not only not important but actively discouraged. Layer effects are inflexible and not suited to picture construction.
Creates a mask. A mask is a non-destructive way or erasing the contents of a layer. This is vital to digital painters and compositors. A mask is often twinned with a selection in the following manner: after a selection is made the mask button is pressed, the subsequent mask being derived from the selection. More in the Selection to Mask Workflow page.
D: Adjustment Layers
Creates an adjustment layer. Adjustment layers are non-destructive versions of the Adjustments that can be found in the Image / Adjust menu. Of the many adjustment layers only Curves and Hue Saturation are really useful to us.
Create a group. A group is a collection of layers which can then be switched off and on separately to the rest of the layer stack. In a complex file you are probably going to need to color these through the contextual menu near the Layer Visibility icon. A Layer Group can also be masked. This enables 'double masking' which can be sometimes very useful useful (e.g. for moving a masked object behind a tree on the background layer). I find the easiest way to create a Group is to make a selection of layers and then select New Group from Layers from the Layer Pallet menu.
Create a layer (or Option Shift N).
Deletes selected layers. More than one layer can be selected for deletion (Command Click to expand selection).
Top of palette
At the top of the Layers Pallet there are some controls that govern the properties of selected layers.
For locking various aspects of the layers. We often need to lock the transparency of a layer when we are painting on it or running a filter. Below in the middle is an image that has been blurred without layer locking. On the right the layer has been locked before the image was blurred. See how the blur was restricted to the bounds of the layer content.
I: Blend Mode
Sets the blend mode of the layer. Vital. Some Blend Modes are very, very, very, very useful.
This sets the transparency value of the layer. Surprisingly, this transparency of a layer hardly ever needs to be changed from the default. If you need to make something lighter then use Curves, if you need to make it more transparent then add a grey layer mask to it. XXX
We never, ever need to change this value. What is the difference between this and Opacity? Google it.
A few (but not many) interesting commands, e.g. select a bunch of layers and the New Group from Layers.
There is little within the layers that can not be accounted for by the icon bars at the bottom and top of the pallet. The exception is the contextual menu set. There are four to deal with, each one appearing according to at what zone within the layer the cursor is.
- The one really useful and unique command in this set is Duplicate Layer. This is great for send a layer over to another file without displacing its position. It also has some Mask commands alo found in the following menu...
- Through this menu we can Delete and Disable the Layer Mask.
- Nothing useful in this menu.
- From here we can change the color of the layer and the Layer Set. This is very useful in establishing file naming and organizing conventions.
Photoshop layering has a syntax: a vocabulary to the way that the layers are arranged. This might be different according to your needs. It is ok if a painting file consists of no more than a little layered compositing (maybe just a few Blend Modes layers clipped to a painted layer), but a compositing file is likely to be more complex. Either way, I wish you to observe the convention that follows. This convention, as well as being a naming agrement, is also a guide to how the compositing structure is organized.
Layer structure conventions
|All layers should have valid names. 'untitled layer 2' is not a valid name. Layer naming as below:|
- A - Content layers
- Always descriptive and start with capitals.
- B - Adjustment layers
- Left to default naming unless otherwise needed.
- C - Blend mode layers
Always simple initials in lower case. Follow this convention:
- D - A simple cloned or painted addition
- Mark as 'Add'.
If your Photoshop file has more than one group of layers (a group being defined as an image layer with multiple adjustment and blend mode layer above it) then the group must be separated by Layer Groups (menu: Layer / New / Group from Layers). Color those groups (right click on group and select color).
By the way… do not clip to layers that are completely opaque. Clipping only works if the layer is at least partly transparent.
Layer and spatial structure
There is, believe it or not, a correlation between the structure of a layer stack and volumetric picture space. Things that are further down in the stack should be further back in space. This make the file easier to organise (e.g. reduce contrast into the depth) and to read.
There is also clear linkage between a layer to which a bunch of other layers are clipping and an object. This 'master clip' layer tends to be an object (figure, house etc). These objects are usually grouped and can be moved around as objects within the scene complete with all their stacked adjustments.
What can go wrong?
The following is based on the kind of things I see in poorly managed student files (and in my own).
- It is possible to name a layer m indicating that its blend mode has been set to Multiply, yet forget to actually set the layer blend.
- One major trouble that people are always having is not knowing where they are in the Layer Pallet. They might be busy painting away on one layer, really thinking that they are in another layer or be painting in the Layer Mask by accident. Do not be fooled by what you see in the Document window. Always be aware of where you are in the Layer Pallet.
- A clipped layer is only necessary if the bottom layer contains some transparency values. If it is completely opaque then dont clip.
- Deciding what is ok to destructively edit and what is ok to non-destructively edit can be a difficult job. Non-destructive editing can very addictive, but it is only necessary if it is necessary (got it?). Tip: layers set to layer blends almost always contain semi-junk information can be be easily replaced. These is no need to non-destructively edit them. Also, it is perfectly ok to merge many painted addition or clone layers.
- The following layer order is wrong:
|Painted or cloned layer|
|Sky content layer|
The painted layer on the top will have been made to match the adjusted layer. If the Adjustment layer is edited then the painted layer will cease to match. far better to do it in this order:
|Painted or cloned layer|
|Sky content layer|
The only problem is that any cloning will be from the values after the adjustment. To deal with this simply switch off the Adjustment layer.
Layer Palette keystrokes
These are the most important Layer Pallet keystrokes to know:
|New layer (with dialogue)||Command Shift N|
|New layer (without dialogue)||Command Shift Option N|
|Duplicate layer||Command J|
|Duplicate layer into another document||Right Click then Duplicate Layer from contextual menu then select destination.|
|Merge layers||Select layers then Command E|
|Make new layer from merged layer stack||Copy all into clipboard: Command A then Command Shift C, then paste: Command V|