I made this shot with the E-30 and Zuiko Digital ED14-35mm F2.0 SWD lens. I set the exposure to Aperture Priority mode, with 21mm focal length. Exposure value was f/22, 1.3s, ISO400, -2.7ev. I developed the ORF file in Olympus Studio v2.3 - which is the latest version - and applied Soft Focus Art Filter effect to give a surreal aura to the image.
A few days back I had been teasing one of my students with some shots depicting star effects on the lamp posts. I compared with a similar shot that did not show the star effect. I did a quick quiz on how I achieved a simple effect without doing any postprocessing tricks or any add-on filters.
He argued that the long exposure was the reason for such effect. I told him, it was not the case. I hinted that the resulting effect was due to the lens behavior, rather than long exposure. He did not agree.
After about half an hour of arguing, I told him it was due to the small aperture, usually at F11 and above. He did not believe me. So, I gave him one night to try it out.
The next day, he agreed that I was right.
Another simple tip to get nice star effect direct from the shot. Nothing else matters.
A comparison of F11 (left) and F5.6 shots. Notice how the star effect starts to diminish as the aperture gets bigger.