In image editing with Photoshop (commonly referred to as PS), understanding layer hierarchy is one of the fundamental concepts that directly determines the display priority and interaction effects of various image elements. Mastering layer hierarchy operations can significantly improve editing efficiency and the precision of your work. This tutorial will combine practical examples to explain in detail the principles of layer hierarchy, adjustment methods, background layer characteristics, and layer deletion techniques. You can also download the sample PSD file to aid your learning.

Core Principles of Layer Hierarchy

Think of layers as "stacked sheets of paper":

• In the Layers panel, layers positioned lower have a lower hierarchy, while those positioned higher have a higher hierarchy.
• Higher layer content directly covers the overlapping parts of lower layers, and lower layers are only visible in areas not covered.

For example, in facial image editing, if the "nose layer" is placed below the "face layer", the "nose layer" will be completely hidden by the "face layer" and become invisible. However, if the "nose layer" is moved outside the pixel range of the "face layer", it will become visible again.

It's important to note: even when a layer is hidden by overlapping content, as long as it's selected (like the "nose layer"), you can still move it using the Move Tool [V]. If you're using the Move Tool and don't see the layer moving without any error messages from PS, you're likely moving a hidden layer.

Two Methods to Change Layer Hierarchy

Adjusting layer hierarchy is a frequently used operation in PS editing, with two main methods: "drag adjustment" and "command/shortcut adjustment", which can be flexibly chosen based on the situation.

1. Drag Adjustment Method (Intuitive and Efficient)

In the Layers panel, directly click and hold the layer you want to adjust (such as the "nose layer") and drag it up or down to adjust its position across multiple layers.

• Example: When moving the "nose layer" below the "face layer", you need to align the destination with the seam between the "face layer" and the "background layer" (refer to the red line in the original diagram), then release the mouse button to complete the hierarchy adjustment.

2. Command/Shortcut Adjustment Method (Precise and Fast)

First, select the target layer, then use commands from the [Layer] - [Arrange] menu or corresponding shortcuts for more efficient adjustment, especially suitable for precise layering adjustments. The commands and their shortcuts are as follows:

• Send Backward: Shortcut [CTRL + [] - moves the layer one level down (one position lower in the Layers panel).
• Bring Forward: Shortcut [CTRL + ]] - moves the layer one level up (one position higher in the Layers panel). Note: "Forward/Backward" can be understood as "layers hanging vertically on a wall facing the user" - higher layers are closer to the user (front), while lower layers are farther away (back). Therefore, "Bring Forward" means raising the hierarchy, and "Send Backward" means lowering it.
• Bring to Front: Shortcut [CTRL + SHIFT + ]] - moves the layer directly to the highest level among all regular layers.
• Send to Back: Shortcut [CTRL + SHIFT + [] - moves the layer directly to the lowest level among all regular layers, but always above the "background layer" (due to the special properties of the background layer, explained below).

Special Properties and Operations of Background Layers

Background layers are a special type of layer in PS with significant differences from regular layers, requiring separate understanding of their characteristics and conversion methods.

1. Three Core Characteristics of Background Layers

1. Fixed Hierarchy: Background layers are always at the bottom of the Layers panel and cannot be moved or have their opacity and fill adjusted.
2. Convertible: Background layers can be directly converted to regular layers; multiple regular layers can also be merged to form a new background layer.
3. Uniqueness and Non-essential Nature: An image can have at most one background layer, and a background layer is not essential (transparent images without a background layer can be created).

2. Methods to Convert Background Layers to Regular Layers

If you need to adjust the hierarchy, move the position, or modify the opacity of a background layer, you must first convert it to a regular layer. There are two common methods:

• Quick Conversion Method: Hold [ALT] and double-click the background layer directly in the Layers panel. The background layer will automatically convert to a regular layer named "Layer 0" (refer to the left image in the original).
• Custom Name Conversion Method: Double-click the background layer in the Layers panel to open the "New Layer" dialog box (refer to the right image in the original). You can customize the layer name (such as "Converted Background Layer"), select "Mode" as "Normal", and click "OK" to complete the conversion.

Creating New Transparent Images Without Background Layers

To create a transparent image without a background layer, follow these steps:

1. Open PS and execute [File] - [New] command to open the "New" dialog box.
2. In the "Background Contents" option, select "Transparent" (refer to the red arrow in the original).
3. Set the image "Width" and "Height" as needed (such as 400 pixels × 255 pixels), "Resolution" (such as 72 pixels/inch), and "Color Mode" (such as RGB Color), then click "OK".
4. After creation, the Layers panel thumbnail will show a completely transparent layer (refer to the green arrow in the original), with a checkerboard pattern representing transparency.

Note: In daily new image creation, "white background" is often chosen because white background is visually more comfortable, while the checkerboard pattern of transparent backgrounds may affect visual judgment during editing. In subsequent learning, white background images are recommended for most scenarios.

Methods and Considerations for Deleting Layers

During the editing process, if you need to delete unnecessary layers, you can use the following methods while paying attention to version differences and maintaining editing flexibility.

1. Four Common Deletion Methods

• Drag-to-Delete Method: In the Layers panel, directly drag the target layer (such as the "eye layer") to the "Trash" button at the bottom of the panel and release the mouse button to delete it. This method doesn't require pre-selecting the layer (even if the current selection is the "nose layer", you can directly drag the "eye layer" to delete it).
• Shortcut Delete Method: First select the target layer, then press the [DELETE] key or [BackSpace] key to delete the layer (ensure the correct layer is selected before deletion to avoid accidental deletion).
• Confirmation Prompt Delete Method: After selecting the target layer, click the "Trash" button at the bottom of the Layers panel, which will open a confirmation dialog "Delete layer XX?". If you check "Don't show again", subsequent deletion operations will execute directly without prompting; to re-enable prompts, execute [Edit] - [Preferences] - [General] (shortcut [CTRL + K] + [CTRL + 1]) and click "Reset all warning dialogs".
• Menu Delete Method: Execute [Layer] - [Delete] - [Layer] command to delete the selected layer. This method is cumbersome and rarely used in practice.

2. Considerations for Deletion Operations

• Selection Confirmation: Except for the "Drag-to-Delete Method", other deletion methods require confirming the correct layer selection (single or multiple) to avoid accidentally deleting important layers.
• Version Differences: In Photoshop CS and earlier versions, the above deletion methods only support deleting single layers; to delete multiple layers, you need to use "Merge Layers" or "Layer Groups" functions learned later.
• Maintain Editing Flexibility: It's recommended in actual production to hide unused layers first (click the "eye" icon of that layer in the Layers panel) rather than deleting them directly. Hiding and deleting produce the same visual effect, but hiding preserves layers for subsequent editing adjustments, maximizing the modifiability of your work.