D
Reset the foreground and background colours to black and white
Alt+[scroll wheel]
Zoom in or out of the image
Cmd/Ctrl+Shift+Alt+E
Create a merged copy of all the layers in the layer stack
Space bar
Temporarily switch the current tool to the Hand tool, for moving around the image while zoomed in
Alt+[eye icon]
Switch off the visibility of all other layers in the layer stack, for before-and-after comparisons
Cmd/Ctrl+I
Invert the colour of a layer mask to black
Shift+[layer mask]
Disable the effects of a layer mask
x
Switch the foreground and background colour swatches
[ or ]
Resize the brush tip
shift+[ or ]
Cycle backwards or forwards through the layer blend modes
Cmd/Ctrl+alt+Z
Undo the last change made to the document. Works multiple times
Cmd/Ctrl+[layer mask]
Load the currently active layer mask as a new selection
Cmd/Ctrl+T
Activate the Free Transform tool
Cmd/Ctrl+J
Duplicate the current layer
Reset the foreground and background colours to black and white
Alt+[scroll wheel]
Zoom in or out of the image
Cmd/Ctrl+Shift+Alt+E
Create a merged copy of all the layers in the layer stack
Space bar
Temporarily switch the current tool to the Hand tool, for moving around the image while zoomed in
Alt+[eye icon]
Switch off the visibility of all other layers in the layer stack, for before-and-after comparisons
Cmd/Ctrl+I
Invert the colour of a layer mask to black
Shift+[layer mask]
Disable the effects of a layer mask
x
Switch the foreground and background colour swatches
[ or ]
Resize the brush tip
shift+[ or ]
Cycle backwards or forwards through the layer blend modes
Cmd/Ctrl+alt+Z
Undo the last change made to the document. Works multiple times
Cmd/Ctrl+[layer mask]
Load the currently active layer mask as a new selection
Cmd/Ctrl+T
Activate the Free Transform tool
Cmd/Ctrl+J
Duplicate the current layer