Having taken a photograph for use as reference material in your painting, you will probably want to edit it so that it is easier to use. This you will probably do using Photoshop.
Indirect reference material you might better know as ‘inspiration’. To my mind inspiration is too vague a term and implies a process over which we have little control.
Photographs can be used as preparatory material, in the same way that sketches and drawings can. They deserve special attention because of the unique place that photography has in painting history.
In the entire history of painting there are very few painters who have relied entirely upon prime source material. In other words, few artists have just stood in front of something and painted it.