This Metabones 1.26x Expander is a lens adapter that allows a Canon EOS EF lens to be used with a FUJIFILM G-Mount GFX camera. While doing so, the adapter's optics help to maximize the connected lens's apparent angle of view, which results in a 0.6-stop decrease for the camera over the lens's aperture range. The Expander supports Phase-Detect autofocus and optical image stabilization (IS), and aperture function is controlled normally by the camera body. Lens focal length and aperture information are adjusted when stored in EXIF data, and one manual lens EXIF profile may also be stored in the adapter.

A Canon EOS EF lens intended for use with 35mm film or full-frame image sensors is mounted to a FUJIFILM G-mount GFX camera, it renders an image smaller than the camera's sensor was built to accept. To avoid instances of vignetting that may result from such a lens and camera combination, this lens adapter enlarges the image before projecting it onto a FUJIFILM G-mount GFX camera's medium-format sensor.

When an image is taken with the Metabones 1.26x Expander for Canon EOS EF Lens to FUJIFILM G-Mount GFX Camera, a matte black internal coating minimizes the potential for reflections inside the adapter barrel, which could otherwise result in unwanted glare within the image. 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 three groups, and a detachable tripod foot is included that features 1/4"-20 threads as well as compatibility with Arca-type tripod heads. For improved prevention of internal ghosting and reflections while further enhancing clarity as well as color fidelity, the lens elements are constructed from high-index lanthanum-based glass.