Adding the Diffusion Effect
Many experienced Photoshop users may already know about this popular effect. For those who don’t know, you can apply a quick version of this effect by duplicating the layer, changing the blending mode to Screen, and applying a Gaussian Blur to the new layer. This tutorial goes further by showing you how to filter out the effect from dark areas and how to restore edge sharpness.
Open a photo to edit.
Duplicate the layer (Layer> Duplicate or Ctrl+J) and change the blending mode of the new layer to Screen.
Add a layer mask to the top layer (Layer> Add Layer Mask> Reveal All).
Make sure the layer mask is activated. The thumbnail of the layer mask in the layers window should have a white border around it. If it doesn’t, click on the thumbnail to activate the layer mask.
With the layer mask activated, open the Apply Image tool (Image> Apply Image). The default settings should be fine. Simply click OK to continue.
Your image should now have a similar glow effect:
Click on the thumbnail of the top layer to deactivate the layer mask. With the top layer selected, open the Gaussian Blur filter tool (Filter> Blur> Gaussian Blur). Make sure that the preview checkbox is checked and increase the radius slider until the desired effect is achieved.