The Add Noise filter in Photoshop works great to make vintage photo effects more prominent and grainy
In this example, without adding noise to the image, the car and pin-up model would appear too ‘clean’.
To add noise to an image, apply a new layer and go to Filter>Render>Clouds (make sure your colours are set to black and white).
Then go to Filter>Noise>Add Noise and check the Monochromatic box.
Change the Noise layer’s blend mode to Soft Light and reduce its Opacity down to 50%.