So many secret handshakes in Adobe Photoshop
Not long ago someone posted on a forum that he was having difficulty with Photoshop’s Merge command. It wasn’t behaving as he expected it to. In the course of helping the poster troubleshoot, I found myself going over the different ways the Merge command is invoked, producing very different results depending upon the state of the layers that are being merged, as well as the modifier keys we use to invoke a Merge command. I thought it might be helpful if I posted a summary here.
To avoid some of the massive confusion about these commands, which have been given a variety of names, I’m relying on the name of each command the History panel uses. The History panel produces a legal document and has to differentiate between each of the Merge commands. When it was developed, these are the names it used. These aren’t necessarily the common names people have used over time, but they are the names I think we might do well to adopt to avoid confusion. To follow along, open the History panel (Window> History) and look at the current state right after invoking one of these commands. I kept the graphic as simple as I could to avoid even more complication.
Cmd-E: Merge Down: This is the primary Merge command which merges the selected layer to the layer immediately beneath it. Layers that don’t allow you to merge a layer into them include Smart Object, Video and Adjustment layers. Vector Shape layers can’t merge into other vector Shape layers, either. However, all of these layers except Video can merge into a normal image layer, whether or not the bottom layer includes transparency. If a mask is present on the bottom layer, a popup message will ask you how you want to handle the mask.
Cmd-Shift-E: Merge Visible: This will merge all visible layers, but it will behave differently depending upon whether or not the bottom visible layer is a Background layer or not. If the bottommost layer can contain transparency (Layer 0, for instance) all the layers are merged without duplicating them into the topmost visible layer. If the bottom layer is a Background layer, it will merge all visible layers to the Background layer without first duplicating them.
Cmd-Opt-E: Stamp Layers: Stamp is another way of saying “make a copy of the layers and merge it onto a layer.” This is not found in the Layers menu or in the Layers panel menu It is one of Adobe’s many secret handshakes. If all layers can contain transparency, it creates a copy of only the selected layers, and merges them to a new layer above the topmost selected layer. You don’t have to create a new layer first.
If the bottom selected layer is a Background layer, it merges a copy of all the selected layers to the Background layer, changing the Background layer itself, but leaving the other layers intact. This command is especially useful if you have a lot of layers, but only want to merge a very few—rather than turning off the visibility for several layers, simply select those few you want to merge.
Cmd-Opt-Shift-E: Stamp Visible: Many people also call this command simply “Merge Visible,” but that doesn’t distinguish it from the actual Merge Visible command found in the Layers panel. This command doesn’t exist in either the Layers panel or in the Layers menu. However, if you hold down the Option/Alt key when accessing Merge Visible from the Layers panel, it will invoke the Stamp Visible command, which you can see reflected in the History panel state.
This popular, though hidden, command copies all the visible layers, merging them, and “stamps” the merged copy to a new layer above whatever layer is currently selected, even a Background layer. You don’t have to create a new empty layer with this command. It will make the layer for you. Of course, if only one layer is visible, Cmd/Ctrl-J to duplicate that layer is the better command.
I hope you find this helpful. Between the lack of menu commands and the variable ways they each behave, the commands can be frustrating. However, they’re worth memorizing. I most often use the Merge Visible and Stamp Visible commands, but there are definitely occasions where Merge Down and Stamp Layers serve my needs.