Guys,
I have attached two photos, both display a Star filter effect. Yet no star filter was used. The first comment anyone makes about these shots is about the use of a Star filter.
The freeway shot was taken with a Schneider 80mm, and the Bridge is taken with a 47mm lens.
Can anyone explain why these shots display a star filter effect when no star filter was used?
Shot at very small aperture?
f11 for the Bridge. Haven't got my Neg sheets on me for the Freeway. However I know the exposure was several minutes for the Freeway, so yes it could have been a small aperture - and the Star effect is more pronounced on this shot, than the Bridge.
Maybe that's it???
It's diffraction off the aperture blades. You get twice as many points as blades for apertures with odd numbers of blades, and equal numbers of points for even numbers of blades.
It's always there, but only shows up clearly when you have a point-like light source which is much brighter than the surrounding scene - streetlights are a classic example.
Is it because those short lenses have really obvious not-round aperture holes? I've got a schneider SA75 in front of me and all apertures have a pentagon/star shaped iris opening except for wide open of course.
Make sure your lens is clean and free of condensation too. Grime or fog on the lens or filter seems to make the point source lights bloom a little bigger.
Exactly.Originally Posted by Struan Gray
I have a print hanging on my wall (from a 35mm XP2 negative) of sunlight streaming through tree branches on a snowy day that shows the same effect for the same reason. People always ask about the star filter on that one, too, but none was used.
Thanks guys that explains everything and is quite obvious when pointed out.
Tony
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