Layer Groups have their own blend mode called Pass Through which allows blending and transparency options to "pass through" the group and effect any layers below the group. To isolate the blending of layers within a group, change the Group's blend mode to Normal.
When on a layer, tap the "/" key to toggle the Lock (Transparency, Pixels, Position, or All) option on and off.
Shift-click on the link icon to temporarily disable linking of a given layer.
Although the basic rules from previous versions of Photoshop still apply, now that multiple layers can be selected at one time in Photoshop, the rules for linking layers have become a bit more complex. They are as follows:
• Selecting a layer that is linked will show the link icon on all the other layers to which it is linked.
• To unlink a single layer from a link set, simply select the layer and click the link icon. If there were other linked layers, they remain linked.
• If none of the layers selected contain linked and you click the link icon, all layers become linked - creating a new link set.
• If the layers selected contain only linked layers, regardless of whether they're all in the same link sets, clicking the link icon unlinks everything selected.
• If the layers selected contain at least some linked layers within the selection, plus any number of unlinked layers, clicking the link icon extends the link set to include the unlinked layers in the selection.
• If the layers selected contains linked layers from two or more link sets plus at least one unlinked layer, everything in the selection gets put into a "new" linked set.
• Layers can only belong to one link set at a time.
To link two or more layers, select them in the Layer's panel and click the Link icon. You can also assign a custom keyboard shortcut using the Keyboard Shortcut Editor to ass a shortcut to Link/Unlink layers. When layers are linked together, commands applied to one layer will also be applied to linked layers (when possible). This includes, moving, transforming, aligning, distributing, apply styles, etc.
Note: before Photoshop had the ability to select multiple layers, linking was more heavily utilized. Now, it is used with complex documents when multiple layers require identical changes thereby eliminating the need to have to reselect multiple layers again and again.
Although I prefer the interactively and simplicity of the Adjustments panel in PSCS4, sometimes I add adjustment layers the "old fashion way" - by Option (Mac) / Alt (Win) -clicking the Adjustment Layer icon on the Layers panel. This method displays the New Layer dialog box which allows for a variety of options including naming layers, color coding of layers and the selection of "blend modes" and opacity.
When working with the Adjustments panel, holding the backslash key, displays a temporary preview of the unadjusted state of a document. (It's like unchecking the Preview check box temporarily - so you have to have made a change to the adjustment for this to work.) Because of the need to distinguish a tap from a hold, there's a slight delay before the results of the hold behavior become visible.
Option (Mac) / Alt (Win) + Shift + O (or double clicking on an image with the keyboard modifiers) will open a flattened version of a file (instead of a layered one) if the file was saved with the Maximize (PSD and PSB) File Compatibility preference turned on. Note: in PSCS4, a dialog will as if you want to "Read the composite data instead?" - click yes to confirm.
When compositing several images into one document I often find that a portion of a layer will end up being positioned outside of the visible image area. Photoshop, of course, is still keeping track of this information (in case I choose to reposition the layer), but when I’m certain that I will no longer need it, I will choose Select > All and then Image > Crop. This eliminates unnecessary information outside or beyond the visible image area and will typically help to keep my file size more manageable
Layer Groups are, by default, set to display blending effects (such as opacity, blend modes etc.) just like any other layer in Photoshop. For example, if a layer in a Group has it’s blend mode is set to “Multiply”, it will be multiplied (blended) with all other layers below it. In this default state, clicking on the Group in the Layers panel displays “Pass Through” as the Group’s blend mode (i.e: any blending applied to layers within the group is “passing through” the group to be applied to the layers below it).
To change this default behavior to limit the blending between layers to only those layers within the Groups, target the Group in the Layers panel and set the Groups blend mode to “Normal” . For even more advanced blending of channels within Groups, choose Layer >Group Properties (or Control (Mac)/ right mouse (Win) -click the Group icon in the Layers panel and select Group Properties) to specify which channels to use for special effect blending of layers.
Not only are Layer Groups great for organizing your layers, you can also use them to mask the contents of multiple layers at a time. With the Group targeted in the Layers panel, click the Add Pixel (or Vector) Mask icon from the Masks panel. This mask will control the visibility of all layers within the Group.
Copying Merged Layers (and Groups)
Command (Mac) / Control (Win) + Shift + C (with a selection) copies a merged view of all visible layers onto the clipboard.
Option-Command (Mac) / Alt-Control (Win) + Shift +E, pastes a merged copy of all visible layers on a (single) new layer above the topmost currently selected layer.
Command (Mac) / Control (Win) -click the disclosure triangle next to a layer Group to expand or collapse all layer Groups in the document.
Option (Mac) / Alt (Win) -click the disclosure triangle to expand collapse all groups nested within the current group.
Option-Command (Mac) / Alt-Control (Win) -cick the disclosure triangle to expand and collapse all groups (nested or not).
Or, if you prefer, Control (Mac)/ right mouse (Win) -click the Group’s disclosure triangle and choose “Close/Open this Group” or “Close/Open all Other Groups”.
To automatically select Layer Groups (as oppose to selecting individual layers), with the Move tool selected, check the Auto-Select box in the Options bar and choose Group from the pull-down menu.
To delete a Group, select Layer > Delete > Group or, with the Group selected on the Layers panel, click the trash can icon. Either method displays a dialog with the options to delete the “Group and Contents” (which deletes both), “Group Only” (which removes any groups but leaves the layers), or “Cancel”.
To delete the Group and all of it’s contents while bypassing the dialog select the Group on the Layers panel and either drag the Group to the trash can icon or, Option (Mac) / Alt (Win) -click the trash can icon.
Command (Mac) / Control (Win) -drag a Group to the trash can icon to delete a Group without deleting it’s contents.
With a Group targeted in the layers panel, Select Layer > Duplicate Group or Option (Mac) / Alt (Win) -drag the Group in the Layers panel (until you see a heavy black line between the layers) and release.
Note this shortcut will not work if the Group is at the top of the Layers panel - in this case, I use the context sensitive menu (Control -click (Mac) or right mouse click) on the Group and select Duplicate Group.
Layer Groups are an excellent way to organize a complex multi layered document. To create an empty Layer Group, click the Create Layer Group (the folder) icon at the bottom of the Layers panel. The Group will be added above the currently targeted layer. If no layers are targeted, Photoshop adds the group to the top of the layer stack.
To create a new Layer Group while simultaneously placing targeted layers into that group Group select Layer > Group Layers or drag the targeted layers (in the Layers panel) to the New Group icon at the bottom of the Layers panel, or use the keyboard shortcut Command (Mac) / Control (Win) + G. The group will be added above the topmost currently targeted layer.
To ungroup layers select Layer > Ungroup Layers or use the keyboard shortcut Command (Mac) / Control (Win) + Shift + G.
Select Layer > Arrange > Reverse to reverse the stacking order of the selected layers. Note: if the layers are in different groups this option is not available.
Command (Mac) / Control (Win) + “[“ or “]” moves the layer up or down. This is a very useful shortcut when recording actions as the specific name of the layer is not recorded.
• Option (Mac) / Alt (Win) + “[“ or “]” targets the layer above or below the currently targeted layer.
• Option (Mac) / Alt (Win) +Shift + “] “or + “[“ adds the next layer up or down to the targeted layer(s) (note when you get to the top or bottom of the layer stack, Photoshop will “wrap around” to continue adding/subtracting layers).
• Option (Mac) / Alt (Win) + “,“ or “.” targets the bottom/top -most layer.
• Option (Mac) / Alt (Win) + Shift + “,“ or “.” targets all layers that fall between the currently targeted layer to the top or bottom of the layer stack.
Note: these shortcuts are essential when recording actions as they help to select layers, but do not record the specific “name” of the layer in the action.
Holding the Shift key while dragging and dropping a layer(s) between two documents will place the “dropped” layer(s) into the center of the destination document. If there is a selection in the destination document, holding the Shift key while dragging and dropping an image will drop it into the center of the selection.
When working with tabbed documents in Photoshop CS4, moving a layer(s) from one document to another can be accomplished by dragging the layers (with the Move tool) from the image area, on top of the “destination” document’s tab. When the “destination” document pops forward, position the cursor over the image area and release to “drop” the layers.
I know that some of you prefer to drag and drop layers from one image to another by dragging them from the Layers panel, however you can not drag and drop from the Layer’s panel to the tab of another open document. If you like the tabbed panels, but feel that you must drag and drop between documents from the Layer’s panel, try using the Arrange Document Icon in the new Application Bar to “Tile All in Grid” all of the open images — then drag and drop from the Layer’s panel to the other tiled images.
I have set a custom keyboard shortcut (Edit > Keyboard Shortcuts) for Window > Arrange > Tile and Window > Arrange > Consolidate to Tabs in order to streamline up the process of toggling between the two display views.
Clipping masks are most commonly used when an adjustment needs to be applied to a single layer in a multi-layer document. For example, if you have a triptych of images (each on their own layer) within a single document and need to brighten only one of the images, you can add an adjustment layer and “clip” it so that it only effects that single layer.
The easiest way to “clip” an adjustment layer to the layer below it is to target the layer that needs the adjustment in the Layers panel, then click the clipping icon at the bottom of the Adjustment panel before adding the adjustment, (or, if you forget, you can click the clipping the icon after adding the adjustment at the bottom of the Adjustment panel). As you make the adjustment, you will notice that the modification is only effecting the layer that the adjustment is “clipped" to.
Another use of clipping masks is to clip content suce as a photo to a shape such as type. In order to do this, put the type layer under the photo layer on the Layer's panel, target the type layer (by clicking in it in the Layer's panel) and select Command-Opt (Mac) / Control-Alt (Win) + G to create a Clipping Mask.
Or, on the Layers panel, hold the Option (Mac) / Alt (Win) key and position the cursor over the line that separates the two layers in the Layer's panel. When you see the icon switch to a triangle with two overlapping circles -click to create a Clipping Mask.
You can have multiple layers clipped to a base layer. Visually, you will know that the layers are clipped because the bottom most layer’s name will be underlined in the Layers panel, and the clipped layer(s) will be indented with an arrow pointing downwards towards the base layer.
To paste content (from the clipboard) into a Layer mask, Option (Mac)/ Alt (Win) -click the Layer mask icon on the Layers panel and then select Edit > Paste.
If you have an active selection in your document (marching ants) and have content on the clipboard, selecting “Paste Into” will paste the content from the clipboard into your selection - and automatically convert the selection into a Layer mask.
Clicking on the Link icon (between the layer and the mask icons in the Layers panel) will unlink the mask from the layer (allowing either to move independently of the other). Click in the empty are to relink the layer with the mask.
To temporarily disable a layer or vector mask, Shift-click the mask icon in the Layers panel. For a Layer mask, simply clicking on the mask thumbnail in the Layers panel will enable it. For a Vector mask, you must shift -click the thumbnail again to enable it. You can also Control (Mac) / Right mouse (Win) -click on the mask in the Layers panel and choose to Enable or Disable the mask.
Clicking on the Vector mask icon in the Layers Panel will toggle the path’s visibility. When the path is hidden, drawing with the Pen or Shape tool(s) creates a new path/shape - as oppose to adding to the mask.
To view a layer mask, Option (Mac) / Alt (Win) -click on the mask thumbnail in the Layers panel. Tapping the “\”(backslash) toggles the display of a layer mask on and off (as a red rubylith overlay). (Looking at the Channels panel, you can see that this shortcut toggles the channels visibility.)
Command (Mac) / Control (Win) + “\” (backslash) targets the layer mask in the Layers panel. Command (Mac) / Control (Win) + 2 targets the layer.
Drag a layer or vector mask thumbnail in the Layers panel to move it from one layer to another.
Option (Mac) / Alt (Win) -drag a layer or vector mask thumbnail in the Layers panel to create a copy of the mask.
Option (Mac) / Alt (Win) + Shift -drag to create copy of a layer mask while simultaneously inverting the mask. (Note: this shortcut does not work with a vector mask - in order to invert a vector mask, select the path with the Direct Selection tool and click the “Subtract From Shapes Area” icon in the Options bar.)
To delete a mask, target it on the Layers panel and click the Trash icon on the Masks panel. If you prefer to click the Trash icon on the Layers panel, or drag the mask thumbnail to the Trash icon at the bottom of Layers panel, adding the Option (Mac) / Alt (Win) key will bypass the option dialog box. You can also Control -click (Mac) or right mouse click on the layer mask and choose discard from the context sensitive menu to bypass the dialog.
To add a mask to a layer, click on the layer or vector mask icon in the Masks panel. If you prefer to use the Layers panel “Add Layer Mask” icon, click once to add a layer mask, click again to add a vector mask, or if you want only the vector mask, Command (Mac) / Control (Win) -click the mask icon. To add a layer mask which automatically hides the selection (as oppose to reveals it as it does by default), Option (Mac) / Alt (Win) -click the icon. Of course with Photoshop CS4, you can always invert a layer mask using the new Invert button on the Masks panel!
Control (Mac)/ right mouse (Win) -click on the eye icon next to a layer (on the Layers panel) to color code a layer. Note: the Background layer will have to be converted to a layer (in the Layers panel, drag the Lock icon to the trash) before color coding.
Thanks for correcting me on this, Mike!