Review by Klaus Schroiff, published September 2016

Introduction

Let's mention this obvious first - this lens is a brick. You may associate mirrorless systems with compact lenses but this one does not qualify - the Leica 100-400mm f/4-6.3 OIS is an example for a substantially smaller super-tele zoom lens. So better prepare your biceps - including an attached camera, the combo stays just below the 2kg mark. The build quality of the Fujinon is very good although it stays slightly short of the best in class (in different systems). The lens body is made of a mix of plastic and metal parts. The broad, rubberized focus and zoom rings operate smoothly but they tend to collect dust like hell. Most Fujinon lenses feature an aperture ring - same goes here but turning it feels a little "grainy". Typical for its class, the lens extends when zooming out to 400mm (+6cm). However, the inner lens tube doesn't wobble. A detachable tripod mount is included but the tripod plate is comparatively small which is odd given the specs of the lens.
All lens elements have a HT-EBC (High Transmittance Electron Beam Coating) which does a good job based on what we've seen. A fluorine coating on the front element helps to repel dust and minimizes smearing. The weather sealing does not only shield against dust and humidity, the lens is also specified to operate down to -10C. A barrel-shaped lens hood is also part of the package and Fujfilm didn't forget to design a window on the hood for controlling a polarizer - a nice attention to detail there. Fujifilm also implemented a transport lock (100mm setting only) and a focus limiter to reduce focus hunting in difficult shooting situations.

The internal AF system uses a "Twin Linear Motor" (LM) - thus a system controlled via two magnets - which provides fast and silent AF operations (note: Fujifilm offer single to quad LMs). As usual manual focusing works by wire thus by driving the AF motor. Fujifilm's optical image stabilizer (OIS) is claimed to be good enough for a gain of up to 5 f-stops. In real world situations, it feels more like 3-4 f-stops but this is impressive nonetheless. The IS can also detect and align its corrective measures to horizontal movements (aka panning). The lens also accepts Fujifilm's 1.4x and 2x tele-converters although at least the 2x converter is probably over the top due to the inevitable effects from diffraction at f/11 (400mm f/5.6 + 2x = 800mm f/11).