Taking day time silhouettes is easy. You just need a dark area with no lighting and an area flooded with natural light. You dont need to open the aperture all the way to f/1.4 for a shot like this. You can have it closed a bit more ... Maybe f/2 or f/2.8. Experiment around. If you let too much light in; you wont get a nice balanced colorful background like in this Silhouetted portrait. .
