About Photoshop masks and Alpha Channels

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When you select a part of an image, the unselected area is "Masked" or protected to avoid being edited. Therefore, after a mask is created, you can isolate and protect the rest of the image when you want to change the color of an area of the image, or apply filters or other effects to the area. You can also use masks when editing complex images, such as gradually applying color or filter effects to images.

Mask example

A.

An opaque mask used to protect the background and edit the butterfly

B.

An opaque mask used to protect the "BUTTERFLY" and color the background

C.

Translucent mask used to color the background and part of the "BUTTERFLY"

Masks are stored in the alpha channel. Masks and channels are grayscale images, so you can use painting tools, editing tools, and filters to edit them like any other image. Areas drawn in black on the mask are protected, while areas drawn in white on the mask are editable.

You can use the quick mask mode to convert a selected area to a temporary mask for easier editing. A quick mask will appear as a color with adjustable opacity. You can use any painting tool to edit a quick mask or use a filter to modify it. After exiting the quick mask mode, the mask is converted back to a selection area on the image.

To store a constituency for a longer time, you can store the constituency as an alpha channel. The alpha channel stores the selected area as an editable grayscale mask on the channel panel. Once a selection is stored as an alpha channel, the selection can be reloaded at any time or loaded into other images.

Storage as the selection of the alpha channel in the channel panel

Note: You can use a layer mask to cover or hide some parts of a layer.