Sunstars

Sunstars (also called starbursts or diffraction spikes) are the radiating lines that appear around bright point light sources — the sun, streetlights, candles — when you stop down the aperture. They are caused by light diffracting around the aperture blade edges.

The number of points in a sunstar depends on the number of aperture blades. Lenses with an even number of blades (6, 8, 10) produce that same number of points. Lenses with an odd number of blades (7, 9) produce twice that number of points (14, 18) because each blade edge creates a spike that overlaps with the opposite edge’s spike.

Most Fujifilm XF lenses have 7 or 9 rounded aperture blades, producing 14-point or 18-point sunstars. The rounded blade design prioritizes smooth bokeh at wide apertures but can produce softer, less defined sunstars compared to straight-bladed lenses.

Sunstar quality depends on stopping down: they typically appear from f/8 and become more defined at f/11-f/16. Wider apertures produce soft, bloomy highlights instead of defined spikes.

For architecture and cityscape photographers, well-defined sunstars add visual interest to streetlight and window reflections. For nightscape shooters, sunstars on bright stars can be a feature or a distraction depending on the composition. Landscape photographers often use sunstars on the sun peeking over a ridge as a compositional anchor.