Made from high grade metal exterior, the Fujifilm Fujinon Teleconverter XF 1.4x TC WR multiplies focal length of lenses by 1.4x. With the lens constructed by seven elements in three groups, this weather and dust-resistant item works well in low temperature. This Fujifilm Teleconverter is compatible with the Fujifilm X-T1 Mirrorless Camera. It is also compatible with the Fujifilm Fujinon XF 50-140mm F2.8 R LM OIS WR lens. Product Features in Detail Focal length increased by 1.4x If the Fujifilm Fujinon XF 50-140mm F2.8 R LM OIS WR lens is used with this teleconverter, it is now equivalent to 107-299mm on a 35mm format. Weather and dust will not bother you When this teleconverter is used, the weather resistance features of the lens and the camera will not affected. Camera autofocus performance is unaffected The autofocus will not change when the teleconverter is mounted. Likewise, accurate focusing at telephoto focal ranges with shallow depth of field as well as shooting at minimum aperture values are still possible. Seven elements in three groups With practically the same lens construction with the Fujinon XF lenses, the teleconverter will not affect image quality.