When done, click OK, and apply the filter again on the other Star Diffusion layer by selecting the layer and pressing Ctrl+F or choosing Filter> Unsharp Mask.
Step 10: Mask the effect out of the foreground
This star diffusion Photoshop effect can interfere with the subject in the photo by covering it. To correct this, we'll simply mask out the effect from the important areas in the photo. Begin by selecting the group in the Layers pallet and then clicking on the Add Layer Mask button in the Layers pallet or choosing Layer> Add Layer Mask> Reveal All. Once you have a layer mask, select the eraser tool and erase the areas that you would like to hide the diffusion effect from. Start with a soft and large round brush with a 50% opacity. The opacity of the brush can be changed from the option bar located near the top of the Photoshop window and the brush settings can be accessed by right-clicking anywhere in the document window.
Step 11: Alter the color of the Star Diffusion effect (optional)
If you want to be more creative, you can alter the color of the star diffusion effect. For example, in the image below, the color of the two layers were changed to make the background bokeh look like it came from a city instead of a park. To alter the color of the effect, select the Star Diffusion layer and adjust the hue with the Hue/Saturation tool (Ctrl+U or Image> Adjustments> Hue/Saturation). Then, select the other Star Diffusion layer and use the Hue/Saturation tool again to change the color. You may also checkmark the Colorize option in the Hue/Saturation tool if you want to use a specific color for the entire layer.
Star Diffusion Photoshop tutorial
Star Diffusion (Different Variation)