Photoshop Post Processing
There are many different ways to make Light Leaks in Photoshop, but most of techniques requieres that you stay with a certain shape or colors. Today, I would like to show you a very easy way to make Light Leaks in Photoshop that you can later use over any of your photos, change the size, shape and even colors of the Light Leak to perfectly match your idea with only 1 single layer.
But first, and if you want to follow this tutorial exactly as described, please download the following free image from Pexels: Download.
Open the image that you want to apply a Light Leak to in Photoshop.
Set your Foreground Color to #b22727 and your Background color to #ff9937.
Go to Layer > New Fill Layer > Gradient. Name this layer as "Light Leak" and click OK.
In the Gradient Fill Window, set the gradient style to Linear, the Angle to 0º, the Scale to 80% and click OK.
With the "Light Leak" layer selected, go to Layer > Smart Objects > Convert to Smart Object.
Press Ctrl+T on your keyboard and in the top toolbar set the Width of the layer to 30% and the Height to 100%.
Go to Edit > Transform > Warp.
Freely drag any of the anchor points or the grid area to make a shape that you like. Once you are happy with the overall shape of your gradient hit the Enter key on your keyboard to commit the transformation.
Go to Filter > Blur > Gaussian Blur. Set any Radius you like for your gradient and click OK.
Note: be sure that the edges are blurred enough so you can't tell where the gradient finish. In this case, a Radius of 30 pixels seems to work fine.
Lastly, with the "Light Leak" layer still selected, change the Blend Mode to "Screen".
If you later want to change the colors of your gradient, simply double click on the "Light Leak" smart object, edit the gradient to your liking, and save the smart object. Also, you can easily edit the shape of it by going to Edit > Transform and pick any of the transformation options in Photoshop to make it look exactly as you want like in the following examples.