This Photoshop tutorial will walk you through how to create light rays from windows that incorporate the correct shadows as made by the frames within the window…
Open your image and duplicate the layer (CTRL/CMD & J)
Open the levels tool (CTRL/CMD & L) and drag the input levels up until only the highlights are left
Select the brush tool, use the black colour and remove all the visible highlights from around the image (also break some of the edges of the window)
Next go to Filter, Blur and choose Radial Blur then chose Amount 100, Blur Method – Zoom and Quality – Draft. Adjust the ‘Blur Centre’ to match the intended beams with the natural direction of the sun through the window. The reason for choosing ‘Draft’ quality is because its quick and allows you to set the direction of the rays which may take multiple attempts. Keep trying this until you get the rough position sorted
In this instance, look at the top half of the window – the rays have gone all ‘blocky’ because there is not enough of a mix of highlights and shadows. This will result in thick, block looking beams of light. We can sort this out easily by rendering a pattern over top
Duplicate layer 1, select a rectangular marquee tool and create a selecting the top window, then go to Filter, Render, Render Clouds – the selection will fill up with a clouded render. Next go to Image, Adjustments, Desaturate to ensure the clouds are black and white. Change the layer type to ‘Linear Burn’, open up the levels tool and drop the slide to adjust the top window to roughly the same brightness as the bottom. You will now see that there is no longer blocks of white but blocks of black and white which will zoom blur nicely!
Merge layer 1 and layer 1 copy then go back to the Radial Blur tool and ensure that its all set – all good? Undo and now change Quality to ‘Best’. Repeat this 3-4 times – each time you will see the rays become more refined
Great, now change the layer mode to ‘screen’
Now open the levels tool and adjust the levels until the beams become proper visible
You can now see that the light beams over stretched over the window frame a little – we need to get rid of this. Create a layer mask and using the brush tool, mask out the overlap.
Et voila, merge and flatten layers – the finished picture!