We need to start with our light. Head to Filter>Render>Lens Flare. You can truly create the light that fits your image’s mood. My general preference is Brightness of 35% and the 105mm Prime flare. Once you’ve dialed in those two ingredients, center the light as best you can on the lighthouse. If it’s not exact, it’s not a problem as we’ll make it perfect in a second. Click OK and you’ll see the Lens Flare appear in your image.
We need to remove the lens flare we just created because as is, we have no control over it (if you’re using Photoshop, you’ve gotta have control, right?) Ctrl/Cmd Z. We’re now going to create a layer for our Lens Flare to live on so Layer >New>Layer or Shift+Ctrl/Cmd+N or click on the New Layer icon at the bottom of the Layers Panel. We now need to fill the layer with gray so Edit>Fill>50% Gray (from drop down menu under content) or Shift F5. Now Crtl/Cmd F to run the Lens Flare filter you just created. You’ll now see the flare you created and have complete control over it.
At this point, I like to paint out the flare elements I don’t want in my photo. These are the colored orbs off some distance from the center of the main lens flare. Select a soft edge brush, click on your foreground color to bring up the Color Picker and in the HSB set the B to 50%. Set your opacity to 100% and paint out the flare. Now, if you’re not sure in the beginning what flare to keep and what to discard, you can skip this step and simply use a layer mask later on to remove unwanted flare. Change the Blending Mode for this new layer to Hard Light and all you see in your image is the flare you just created, the beginning of your light.
At this point, you can stop and say you’re finished. If you were to capture the lighthouse light coming straight at the lens, this is generally what you’d capture. If you want to have the beam of the lighthouse, we need to do a couple more steps.
Grab your Marquee Tool (tap M key) and draw a box around your light. We now want to inverse our selection Select>Inverse of Shift+Ctrl/Cmd+I. Then tap the delete key. Reverse the selection with Shift+Ctrl/Cmd+I. This makes it easier to manipulate the light in the next step. At this point, make your image smaller with Ctr/Cmd+- so we can stretch out our light.
Your selection is still active from the last step. Now we’re going to use Free Transform Ctrl/Cmd T to stretch our light. You’re going to stretch a WHOLE lot! Once you have your light stretched to taste, enlarge the image so you can move the light so that the bright center is over the light of the lighthouse. Since we’ve put this in its own layer, you can always fine tune the placement of the light with the Move tool later.
At this point, add a Layer Mask to the light layer. With a soft edge brush, 100% opacity and painting with black, paint out the elements of the light you don’t want. Remember, it’s a layer so you can modify the light any time, any way you like. For example, if the light is too bright, just lower the layer’s opacity