What causes ring-shaped or 'soap bubble' bokeh besides mirror lenses?
Asked 6/30/2018
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I’ve seen photos with bright outlines around out-of-focus highlights that look like ring-shaped bokeh. Mirror (catadioptric) lenses are known for donut-shaped bokeh, but these examples don’t seem to have been shot with a long mirror lens. What other lens traits or setups can produce this kind of effect?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
8y ago
2 Answers
10
The doughnut bokeh of catadioptric ("mirror") lenses is not caused by the rear mirror or long focal length, but by the obstruction (front mirror actually) on the front element.
You can achieve it with any lens if you put a round sticker on the front lens. Or better: on a clear (e. g. UV) filter in front of it.
With a little practice you could even achieve a heart or star shaped bokeh.
Originally by user62463. Source · Licensed CC BY-SA 4.0
user62463
8y ago
0
Generated from our catalog & community — verify before relying on it.
Ring-shaped bokeh can come from two different causes.
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Central obstruction: Mirror lenses create donut bokeh because part of the lens is blocked in the center. A similar effect can be produced artificially by placing a circular obstruction on a front filter or lens opening.
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Soap-bubble bokeh: Some lenses produce bright-edged out-of-focus highlights due to over-corrected spherical aberration. This is often called soap bubble bokeh and is associated with certain older optical designs, especially Cooke Triplet-type lenses. Meyer-Optik Trioplan lenses are a well-known example.
So if the photos weren’t taken with a mirror lens, the most likely explanation is a lens with strong soap-bubble rendering rather than true donut bokeh from a central obstruction.
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