Metabones T Speed Booster Ultra 0.71x Adapter for Canon Full-Frame EF-Mount Lens to Sony E-Mount APS-C Camera - allows a full-frame Canon EF-mount lens to be mounted onto a Sony E-mount camera. While doing so, the adapter's optics help to maximize the connected lens's apparent angle of view while providing a 1-stop increase for the camera over the lens's aperture range.

If a lens intended for 35mm film or similarly sized full-frame camera sensors is connected to a camera with a Sony E-mount APS-C-sized sensor, it would project an image larger than the Sony E-mount APS-C sensor was built to accept. Able to capture only the center portion of the projected image, the effective angle of view of the lens would be narrowed, creating an in-camera "crop factor." The T Speed Booster Ultra 0.71x Adapter for Canon Full-Frame EF-Mount Lens to Sony E-Mount APS-C Camera condenses the light from a lens designed for 35mm film or "full frame" camera sensors and projects it onto a Sony E-mount APS-C sensor. This allows a Sony E-mount APS-C sensor to utilize more of the light gathered by a connected lens, which effectively reduces the crop factor while making available to the sensor an additional 1 stop of light for each of the lens's f/stop settings.

This adapter is constructed from aluminum alloy for durability while minimizing weight and its mounting rings are made with brass to further prevent wear-and-tear. Inside are five lens elements in four groups that are designed to provide optical clarity as well as color fidelity, and a detachable tripod foot is included that features 3/8" threads as well as compatibility with Arca-Swiss tripod heads.

The T Speed Booster Ultra 0.71x Adapter for Canon Full-Frame EF-Mount Lens to Sony E-Mount APS-C Camera supports electronic communication between an attached camera and lens. If the lens includes autofocus, image stabilization, as well as camera-controlled aperture functions, this adapter is intended to allow those features to be used. If an attached lens is also capable of generating EXIF metadata when used with a directly compatible camera, the T Speed Booster Ultra 0.71x Adapter for Canon Full-Frame EF-Mount Lens to Sony E-Mount APS-C Camera is designed to allow that information to be saved along with image files generated with a combination of the lens, a Sony E-mount camera, and the adapter.

By enabling camera-controlled aperture functions for a Canon EF-Mount Lens when used with a Sony E-mount camera, program, shutter-priority, aperture-priority, as well as manual modes can be set and used through the camera. Power for these functions is transferred from the camera to the lens, and the T Speed Booster Ultra 0.71x Adapter for Canon Full-Frame EF-Mount Lens to Sony E-Mount APS-C Camera is designed to accomplish this in an energy-efficient manner. When manual focusing is preferred with a compatible electronic lens, an integrated switch can be depressed which opens the lens's aperture diaphragm to it largest setting. The resulting shallow depth-of-field can then be used to help ensure focus accuracy.

While the T Speed Booster Ultra 0.71x Adapter for Canon Full-Frame EF-Mount Lens to Sony E-Mount APS-C Camera is intended for Sony E-mount cameras with APS-C sized sensors, it may also be placed on "full frame" Sony E-mount cameras as well. However, such cameras must be set to "crop mode" when combined with this adapter to avoid generating images with vignetting.