Built in Star Filter
- Purple pier behind the dunes at Jockeys Ridge State Park in Nags Head North Carolina.
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All lenses have a built in star filter. To get the star effect stop your lens down to a very small aperture opening (large f-stop number). Any small pinpoint of light will become a star. Lens apertures are constructed of blades and the number of blades determines the shape of the aperture.The number of points on the star reflects this shape. By counting the number of points you can tell how many slides the aperture opening has. If you’re star has eight points then the aperture opening is an octagon. More expensive, better quality lenses have more blades in the aperture, to keep the aperture as round as possible. This helps make the boca (out of focus areas in a photograph) more pleasing. Wide-angle lenses seem to work best for this technique because the light source has to be small or a pinpoint in the photograph.