Optical adapter with reduction optics for lenses; shrinks crop factor and gains approximately one stop of light.
Technical Details
Speed Boosters reduce the focal length by 29% (0.71x factor) and increase the aperture by exactly one stop. A 50mm f/1.4 Canon EF lens becomes a 35mm f/1.0 equivalent on a Speed Booster. The internal optics consist of 4-5 aspherical elements with special coatings. Metabones produces variants for Canon EF to Sony E-mount, Canon EF to Micro Four Thirds, and other combinations. The XL type offers a 0.64x reduction for even more extreme wide-angle effects. Typical dimensions: 75mm diameter, 25-30mm height, weight between 200-350g depending on the model.
History & Development
Metabones introduced the first Speed Booster in 2013, developed by Caldwell Photographic. The goal was to use full-frame lenses on smaller sensors without suffering the typical crop disadvantages. In 2014, the Speed Booster ULTRA followed with improved optics and reduced vignetting. Viltrox, Zhongyi Optics, and other manufacturers brought more affordable alternatives to market between 2016-2018. Since 2019, electronic variants with autofocus support for specific camera-lens combinations have been available.
Practical Use in Film
Speed Boosters allow the use of expensive full-frame lenses on Super35 or MFT cameras, achieving a more authentic full-frame look. They compensate for the crop factor of cameras like the Blackmagic Pocket Cinema Camera or Panasonic GH series. In low-light shooting, the additional stop of aperture offers crucial advantages. Documentary filmmakers use them for compact kits with professional optics. The depth of field is minimally altered by the focal length reduction, and the bokeh characteristics are largely preserved.
Comparison & Alternatives
Unlike standard lens adapters, which only provide mechanical adaptation, Speed Boosters actively alter optical properties. Simple adapters crop the image more severely and reduce the effective light intensity. Full-frame cameras like the Sony FX6 or Canon C70 eliminate the need for Speed Boosters but are larger and more expensive. For pure wide-angle applications, native ultra-wide-angle lenses often offer better image quality than Speed Booster combinations with standard focal lengths.