The danger with photographs is that one tends to copy them, and copying, while admirable for record, is not really creative. Paintings made from photographs often look rather stilted because they lack the 'time element' evident in work made from life. By 'time element' I mean the generalisation and selection process that is a necessity if you are painting from life over a period of time, whether it be minutes, hours or days, because the light and shadow changes and things move. Paintings do not have to look perfect, and they certainly do not have to look like photographs to be successful, in fact they are more appealing if they don’t!
Using several photographs together for your reference can help avoid becoming a slave to the limited information of one photo, a sequence of photos will help you realise that things change and help show what matters and what doesn’t, that you can leave lots of things out without losing any of the punch. If I am working from photographic reference I tend to work from several photographs at once, flicking back and forth between them. I also place the photographs/computer screen at a small distance away from me and upright in front of my gaze, so they are in the same eyeline as if I was observing 3 dimensional life.
The eye sees the subtleties of light and shade but the camera sees tones rather starkly. Shadows may look very dark in a photo and even black, but apply some logic, unless the shadow is really underneath and devoid of all light it probably wasn’t black at all because the ambient light would have enabled your eye to see more colour in the shadow than the camera can. And shadows move quite swiftly, so don't allow a shadow to be too static in your painting either. People tend to believe that the photo must be right, but why would you trust such a small portion of reality? So use them as a guide, feel no obligation towards them or their supposed veracity, take things from them such as shapes and spaces, but work out your own colour set and the relative tones. Question what you include and leave everything out that is not relevant to your painting. The upside of photographs is that they do not move or go away, so you have plenty of time to experiment and master your techniques!