I have seen a lot of video tutorials and guides for both compositing and creating fake bokeh. In my experience, the bokeh invariably looks fake and can ruin an otherwise promising composite. However, in this video Serge Ramelli demonstrates how to use Photoshop’s own bokeh creating filter ‘field blur’.
I was unfamiliar with this method until recently and I’ve now had a chance to try it myself. All that is necessary for you to create very realistic bokeh that looks as if it is fresh from some expensive and fast glass is an image of lights. As Serge uses in this video, a cityscape image is perfect although I also had success with an image of Christmas tree lights and fireworks.
The second noteworthy lesson in this video is the quick but effective method for cutting out a subject for a composite, adding them to an image and adjusting the white balance so that they fit the backdrop.