Characteristic bokeh from mirror lenses (300–1000mm, f/5.6–f/11) rendering out-of-focus highlights as ring-shaped donuts with transparent centers.
Technical Details
Mirror lenses use a combination of lenses and mirrors for light refraction. The central secondary mirror typically has 30-40% of the diameter of the primary mirror. Common focal lengths range from 300mm to 1000mm with fixed apertures from f/5.6 to f/11. The annular aperture is created by the shadowing of the central mirror, which renders point light sources as donuts with a diameter-to-hole ratio of approximately 3:1. In bright reflections or light points in the out-of-focus area, concentric circles with a distinct edge and a transparent center are produced.
History & Development
The first photographic mirror lenses emerged in the 1940s, based on astronomical telescope designs. Rubinar introduced the first mass-market 500mm f/5.6 mirror lens in 1960. In the 1970s and 1980s, manufacturers like Tamron, Sigma, and Tokina established themselves with 300mm to 1000mm variants. The film industry first intensely discovered the characteristic bokeh effect in the late 1970s. Modern versions have also been available since 2010 as adaptable vintage lenses for digital cinema cameras.
Practical Use in Film
Soap bubble bokeh creates a surreal, dreamlike atmosphere and is specifically used for flashback sequences, memory scenes, or psychedelic moments. Ridley Scott used it in "Blade Runner" (1982) for the dystopian city scenes with the characteristic light rings. The technique is particularly suitable for night shots with many light points – streetlights, neon signs, or candles transform into floating rings. The workflow requires precise focusing, as the fixed aperture does not allow for depth-of-field correction. Autofocus usually does not function reliably.
Comparison & Alternatives
In contrast to the creamy bokeh of modern telephoto lenses, soap bubble bokeh appears significantly more graphic and unnatural. Anamorphic lenses produce oval bokeh shapes, while apodization filters create smooth transitions. Digital post-production can simulate similar effects but does not achieve the organic unpredictability of true mirror optics. Modern alternatives include special bokeh filters or custom apertures, which, however, only represent approximations. Soap bubble bokeh remains unrivaled for surreal, fairytale-like, or nostalgic imagery.