Released in 2016 alongside the Sony FE 70-200mm f/2.8 GM OSS and Sony FE 1.4x Teleconverter, the Sony FE 2x Teleconverter is an essential addition to Sony’s full-frame E-mount lineup. Given the relative lack of dedicated telephoto options available to the mount, the Sony FE 2x Teleconverter dramatically enhances the versatility of the lenses it is compatible with: the Sony FE 70-200mm f/2.8 GM OSS, the Sony FE 100-400mm f/4.5-5.6 GM OSS and the recently released Sony 400mm f/2.8 GM OSS. The teleconverter maintains full communication between the lens and the E-mount mirrorless camera body it’s mounted on, which ensures the proper function of the camera’s exposure metering, autofocus, and image stabilization. The 8 element / 5 group optical design includes one Aspherical Element to minimize chromatic aberration while maximizing resolution. Additionally, Sony claims the lens is dustproof and moisture resistant, which means it should continue working well when used in inclement weather conditions. However, the dramatic teleconverter effect comes with some distinct penalties, including a loss of 2 stops of brightness compared to your lens’s usual maximum aperture, along with a reduction in overall image quality. While all 2x teleconverters degrade the quality of an image, some are better made than others, with the high performing Canon’s EF 2x III Teleconverter coming to mind. I was keen to see if the Sony FE 2x could perform at the same high level and especially intrigued by the prospect of paring it with the FE 100-400mm f/4.5-5.6 GM lens and Sony Alpha 9 camera body.