The M42 Lens to Sony E-Mount Camera Lens Turbo Adapter Mark II from Mitakon allows M42 lenses to be mounted on Sony E-Mount APS-C format cameras, increasing the angle of view by 0.726x and the maximum aperture of the lens by 1 f-stop.
The four optical elements of the Lens Turbo adapter condense light from the M42 full frame lens and project it onto the camera's APS-C sensor allowing the sensor to capture all of the lens' transmitted light, negating the 1.5x crop factor and effectively producing full-frame coverage on non-full-frame sensors. A corresponding increase in the maximum aperture of 1 f-stop makes the lens more effective in low-light situations.
The Mark II version of the Lens Turbo features an improved design to produce sharper images. Its rectangular rear lens rests closer to the camera's sensor improving light transmission and an enhanced lens coating minimizes ghosting and flare. One extra-low dispersion (ED) lens element reduces aberrations for better delineated images. The adapter offers a sturdy metal construction and stainless steel mounts, it attaches to both camera and lens with little play and includes a front and rear protective cap. The Lens Turbo is a manual adapter offering no electronic communication between lens and camera.
The Lens Turbo adapters are compatible with APS-C sized sensors. Although they will physically fit the Sony full frame mirrorless cameras, the camera must be set to Crop Mode to fully support the speed booster's functions.