You can either read through this here, or watch the video tutorial
Ok. This is a very quick rundown on how to create a spotlight effect – and not an actual tutorial. Hope you don’t mind me posting it here anyway.
I snagged this image of Zhang Ziyi and applied a filter to it.
Open your image in photoshop and make sure it is set to RGB color (image -> mode -> rgb color) and duplicate the base once.
Then go to filter -> render -> lighting effects. A window will open.
This is a link to a screenshot where I already explained the basic functions in there. It might help to check it out.
And these are the settings I applied in this example:
After that I reduced the opacity to 83%.
This was the result:
Edit: the brushes I used in the preview were created by ca_pris