Remove the Subject From the Background
When adding motion blur to a photo, it is important to blur only the background. The subject should stay un-blurred to make them stand out from the background.
In order to blur the Background and not the subject, the two elements must be separated first. The easiest way to separate the subject and Background is to remove the subject from the background.
Paint over the subject and the Tool will fill them in with information from the background. This doesn’t have to be perfect, after all, you will be applying a blur to the background. The main goal is to make sure the subject is not blurred with the background.
Add Motion Blur to the Background
With a Smart Object you can use Smart Filters, and when adding a blur of any kind, it is best to be done as a Smart Filter. Smart Filters can be changed at any time, making them more versatile and less destructive.
It is time to add the blur to the Smart Object. The type of blur will change depending on the Motion of the photo. In this case, we use a simple “Left-to-Right” Motion Blur because the subject is moving horizontally across the image.
If the subject in your photo is moving towards or away from the camera, choose a Path Blur and create paths in the direction of the movement.
Reveal the Subject
After applying a Motion Blur or Path Blur to the background, it is time to reveal the original subject. Lower the Opacity of the layer to about 80% and add a layer mask to the blurred Smart Object. Paint black on the Layer Mask over the original subject to reveal them through the Smart Object Layer.
Take your time to create an accurate selection around the subject. After completing the layer mask, change the Smart Object layer Opacity to 100% and you are done!
To change the amount of blur on the background, double click on the Blur Smart Filter, and adjust the blur amount. The Layer Mask will stay intact, revealing the subject and provide an instant preview of the Background blur with a still subject.