Layers referencing in Photoshop CS5 (12)?

Question

I have two layers L1 and L2. I want to make layer L3 to copy L1 and L2 every time when they modifed. L3 may contains some filtering and every time when I modify L1 or L2 my L3 must recopy modified layer and reassign it's filtering to new image. How to make it in photoshop CS 5?

Answer 1

You can't really do this with straight layers.

But you can do this with a smart object.

1. Create Layer 1 and Layer 2.
2. Highlight both layers in the Layers Panel and right-click (Win) or control-click (Mac) on the highlighted layers
3. Choose "Convert to Smart Object"
4. You'll see that the two layers are now one smart object layer

5. To edit the original two layers, simply double-click the Layer Thumbnail for the Smart Object. A new window will open with your two original layers.

   Any edits will be reflected in the smart object when you save.