Optical adapter between lens and sensor. Reduces effective focal length and gains roughly one stop of light — lets vintage glass work on digital cameras without brightness loss.
Technical Details
The Speed Booster uses a specially constructed 4-element converging lens group with a 0.71x reduction, which concentrates the light from the larger image circle onto the smaller sensor area. This leads to an exact one-stop increase in light sensitivity – f/2.8 effectively becomes f/2.0. Available variants include adaptations from Canon EF to Sony E-mount, Canon EF to Micro Four Thirds, Nikon F to various mounts, as well as special versions for Leica R and Contax lenses. The optical design retains 99% of the original lens resolution.
History & Development
Metabones introduced the first Speed Booster in 2013 as a revolutionary solution to the crop factor issues prevalent with mirrorless cameras at the time. The concept was developed by Caldwell Photographic Inc. in collaboration with German optics specialists. In 2016, the Ultra version followed with an improved optical formula and reduced vignetting. The current Cine Edition (2019) offers additional features such as electronic aperture control and more precise mechanical tolerances for professional film productions.
Practical Use in Film
Speed Boosters allow the use of high-quality full-frame lenses on more compact cameras like the Sony α7S or Panasonic GH series without losing their characteristic look. In documentaries, cinematographers appreciate the gained light sensitivity in available-light situations. Netflix productions frequently use Speed Boosters on Micro Four Thirds cameras to reduce the weight of rig setups without having to forgo full-frame optics. However, the adapter causes minimally increased chromatic aberration in the image corners and requires precise calibration for focus-pulling systems.
Comparison & Alternatives
Unlike conventional lens adapters, which merely provide mechanical compatibility, the Speed Booster actively alters optical properties. Viltrox and Zhongyi offer more affordable alternatives with a similar 0.71x reduction, but with lower optical precision. Modern alternatives include native full-frame lenses for mirrorless systems, which are significantly more expensive. For pure crop-sensor productions without full-frame legacy, specially developed APS-C lenses often offer a better cost-benefit ratio than Speed Booster combinations.