Today’s Question: I totally agree with you that I never want to use the flatten function in Photoshop. Sometimes, though, I want to select exactly what I see on the screen for an area, but going to the top layer, even with “Current and Below” it doesn’t grab what I’m seeing. I have to flatten the image, make my selection, copy the pixels, and then undo the flattening. This works but it’s both inconvenient and a little risky that I’ll somehow do something wrong and lose the layers.
Tim’s Quick Answer: This is a good example of a situation where you would want to use a new “Merge Visible” layer. This is a layer that represents the composite contents of all layers below, which you can then add a layer mask to if you only want the effect to impact a portion of the photo.
More Detail: This question was a follow-up to an answer earlier this week about flattening images in Photoshop. As I mentioned in my original answer, I prefer to never flatten a master image. Instead, I keep all layers intact to maximize the flexibility of my workflow.
In some cases you may find that you can’t really work with certain features (such as filters) when you have multiple image layers. In that type of scenario you can instead use the “Merge Visible” command to create a layer that represents the net result of all layers below.
To get started, click on the thumbnail for the top-most layer on the Layers panel to make that layer active. Then click the “Create New Layer” button (the blank sheet of paper icon) at the bottom of the Layer panel to create a new empty layer at the top of the layer stack.
Next, go to the Layer menu on the menu bar. Press and hold the Alt key on Windows or the Option key on Macintosh, while selecting “Merge Visible” from the Layer menu. This will cause the composite contents of all visible layers below to be created on this new layer (rather than flattening all visible layers).
Note that because the “Merge Visible” command applies only to visible layers, you can prevent certain layers from being included by simply turning off the visibility for those layers.
You can then apply any effects you’d like to the new composite layer. If needed, you can also add a layer mask so this layer is only visible in certain areas of the image. Note that because this layer will block all layers below, if you need to make changes to any work you performed before creating the “Merge Visible” layer, you’ll need to turn off the visibility for the “Merge Visible” layer to be able to see the effect. You might also need to create a new version of the “Merge Visible” layer so that it will reflect any changes you’ve made to layers below.