I captured this photograph at the Sandy Utah city hall building this week. The city decorates each of the front lawn trees with small lights every year during the Christmas holiday.
To create the effect, I photographed this with a telephoto lens set wide open’ (f/4.5) and got as close to the tree as possible (while still being able to achieve focus on it). Due to the low light, this took a rather long exposure of nearly 1/2 of a second and a tripod was used. If the lens was not set wide open the circles would have taken the shape of octagons (reflecting the shape of the lens aperature).
The result of the background lights blurring into circles and overlapping creates a dramatic effect.