Create alpha channel masks

Last updated on Oct 6, 2026

Learn how to use the Channels panel to build custom masks by painting with black, white, or gray values.

Building alpha channel masks from scratch gives you precise control over which areas of your image remain editable and which are protected during adjustments, filters, or color changes.

Create alpha channels when you need to build a mask manually using painting and editing tools rather than converting an existing selection. This approach works well for gradual transitions, complex masking scenarios, or when you want to refine a mask iteratively. To save existing selections as alpha channels, see Save and load selections. To understand how alpha channels store and manage masks, see About masks and alpha channels.

Alpha channels appear at the bottom of the Channels panel as grayscale thumbnails. Once created, you can paint directly on the channel using any painting or editing tool, or modify it with filters. Areas you paint black become protected (masked), areas painted white remain editable, and gray values create partial transparency for smooth transitions.

Create a channel with default settings

Open the Channels panel by selecting Window > Channels.

Select the New Channel button at the bottom of the Channels panel.

A new alpha channel appears at the bottom of the panel with default settings (masked areas shown in black, selected areas in white).

Create a channel with custom settings

Alt-click (Windows) or Option-click (macOS) the New Channel button at the bottom of the Channels panel.

In the New Channel dialog, enter a descriptive name for your channel.

Choose whether Masked Areas or Selected Areas determines how black and white values are interpreted in the channel.

Select the color swatch to choose an overlay color that contrasts with your image, then adjust the opacity slider to control overlay visibility.

Select OK to create the channel.

Tip

The overlay color and opacity only affect how you view the mask while working—they don't change how the mask protects your image.

Paint on the channel to define the mask

Select the alpha channel thumbnail in the Channels panel to make it active for editing.

Select the eye icon next to the composite color channel (RGB, CMYK, or Lab) at the top of the Channels panel to display your image with the mask overlay.

Select a painting or editing tool from the toolbar.

Paint with white to remove areas from the mask and make them editable, or paint with black to add areas to the mask and protect them.

Paint with gray values to create partially transparent areas—lighter grays allow more editing through, darker grays provide more protection.

Adjust the Opacity setting in the options bar before painting to build up the mask gradually.

When you finish painting, select the composite color channel to return to normal editing mode. Your alpha channel mask remains stored in the Channels panel and can be loaded as a selection, refined further, or used with adjustments and filters.

To modify an existing alpha channel's settings, double-click the channel thumbnail in the Channels panel or select Channel Options from the panel menu.

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