Today was the first really warm spring day of the year and I wanted to experiment with my lenses to catch the afternoon sun with star effect.
How to photograph a sun star? A sun star is caused by the phenomenon of diffraction, when light is passing a narrow opening or gets deflected at an edge. The small opening is given with a lens when setting it to a high F-Stop (e.g. F16 and higher). Depending on the construction of the lens diaphragm, the stars can have different shapes. Also there can be unwanted lens flares, depending on the quality of the lens coating.
The design of the aperture diaphragm has a profound effect on the star effect. An even number of aperture blades creates an even number of spikes (e.g. 6 blades create 6 spikes), an odd number of blades create the double number of strikes (e.g. 7 blades create 14 spikes).
The following tips are useful when experimenting with sun stars:
- Set the aperture to a higher F-stop. It is known that a high F-stop means also a high depth of field. It is important to know, that also because of diffraction the images tend to lose sharpness at a high F-stop. Depending on the image you want to shoot, keep in mind that a very high F-stop brings the best sun star and depth of field, but also brings you loss in quality. Especially for landscape photography stay away from high F-stops or take several pictures and combine them to one image in your post processing..
- Figure out which of your lenses produce the best sun star. The better the optical dedign, the sharper the sun star will be. Sun Stars can't be shot with smartphone lenses!
- Remove the UV filter to avoid lens flare.
- Clean the lens, as dust spots become more visible in back light.
- Set the star off-axis, don’t point directly into the sun (safety for eyes and camera)
- The longer the exposure, the more star effect will be visible (but don't overexposed).
- Bright sky and clouds will produce less of a star effect than if in a deeper blue sky.
- The sun star can be made larger by zooming in.
- Partially blocking the light from the sun, e.g. by a tree or a person will give a more dramatic sun star.
Here is my test images with my lenses that I took just around in the neighbourhood.
The first image is taken with a CANON lens 50mm, F1,8 with 7 aperture blades (14 strikes).
The second image shows a sunstar with 6 strikes. I used a Canon lens EFS 18-55mm, F3,5-5,6 ISII, the diaphragm has 6 blades.
The third image is made with a Canon lens EFS 10-18mm, F4,5-5,6 (7 blades).
The last images is taken with a Sigma lens 18-250mm, F3,5-6,3 DC Macro OS HSM (7 blades).
The table below shows the sun stars in detail.