Sometimes a flash can be too splashy, for example I often find myself wanting to pick one person out of a crowd in a party environment. In the picture above I wanted to highlight the girl while keeping the father lit but on the periphery of the image. The rest of the photo I wanted to keep as dark as possible for emphasis.
To get this effect I have a cut down Pringles tin stuffed full of cut down drinking straws. The whole assembly slots over my flash head, (and is held in place by the plastic Pringles lid with a suitable hole cut into it to allow it to push snugly over the flash head). The straws then act as “light pipes” to direct the flash light on the required target. The entire assembly is covered with electricians tape for a modicum of professionalism. I used coloured drinking straws from Ikea but they do add some colour to the light. On reflection black straws would be better.
Here is the colour version, only processing here is a S curve to give some contrast: