This tutorial will show you how to use Photoshop’s Lens Blur filter to make the background appear out of focus.
Step 1: Bring two images together
When you have your two photos selected you need to cut your portrait out from its original background. One of the easiest ways to do this is to select your subject with the Quick Selection Tool then go to Select>Inverse, Edit>Cut to remove the background. You then need to go back to Select>Inverse to select your subject again and go to Edit>Copy. From here make sure your landscape shot is open and create a new layer above it in the layers palette. Make sure the new layer is selected then go to Edit>Paste and your person will now be pasted into the new layer.
Step 2:Lens blur
Our person may now be sat on their new background but the image doesn’t look quite right. The background needs blurring slightly and we are going to use a Lens Blur filter to do this. Make sure your background layer is selected then go to Filter>Blur>Lens Blur.
A new window will open and you need to adjust the Iris Radius slider until you’re happy there’s enough blur in the image. You can also tweak the Specular Highlights Threshold and Brightness settings to add a bit of lens flare and a little pop to the highlights if you want to. Hit OK and wait for the changes to be applied.
And that's your image complete.