Sony’s new telephoto zoom brings faster autofocus and constant aperture
Sony has introduced the FE 100-400mm F4.5 GM OSS, a new full-frame E-mount G Master lens aimed squarely at photographers who need reach, speed and consistency in one long zoom. On paper, this feels like a serious step up for wildlife, birding, sport and photojournalism shooters, especially those who want the flexibility of 100-400mm without the exposure shift of a variable-aperture design.
The headline is the constant F4.5 maximum aperture. That matters because, whether you are at 100mm or fully extended to 400mm, the lens holds the same maximum aperture. For anyone following a footballer down the touchline, a bird across changing light, or a subject moving through a cluttered background, that consistency should make exposure and depth-of-field decisions feel more predictable. Sony says the optical design uses ED XA, XA, Super ED and ED elements to control chromatic and spherical aberration, with Nano AR Coating II to reduce ghosting and flare.
Autofocus is another major part of the story. The lens uses four XD Linear Motors, a floating focus mechanism and updated AF algorithms, with Sony claiming autofocus up to three times faster and subject tracking improved by up to 50% compared with the FE 100-400mm F4.5-5.6 GM OSS, when used on the Alpha 9 III under Sony test conditions. It is also compatible with up to 120fps continuous shooting with AF/AE tracking on the Alpha 9 III, which makes its intended audience very clear.
I’m also pleased to see Sony focusing on handling rather than just headline numbers. At 1,840g, this is not a small lens, but the inner-zoom construction means the barrel length and centre of gravity remain stable as you zoom. That should make a real difference when panning, shooting handheld for long periods, or working from a monopod in tight sideline spaces. Sony has also included optical stabilisation, support for Active Mode on compatible bodies, four focus hold buttons, a function ring, a zoom smoothness switch, a dust and moisture resistant design, and a fluorine coating on the front element.
For extra reach, the lens works with Sony’s 1.4x and 2x teleconverters, extending it to 800mm with the 2x converter, or up to a 1,200mm equivalent field of view in APS-C mode. That makes the FE 100-400mm F4.5 GM OSS look like a premium, highly specialised option for photographers who want fast telephoto performance without stepping into a large prime lens setup.
Sony FE 100 400mm Specifications
Mount: Sony E-mount
Format: 35mm full-frame
Focal length: 100-400mm
APS-C equivalent focal length: 150-600mm
Maximum aperture: Constant F4.5
Minimum aperture: F32
Lens construction: 28 elements in 20 groups
Aperture blades: 11, circular aperture
Minimum focus distance: 0.64-1.5m
Dimensions and weight: 119.8 x 328mm; 1,840g
Sony FE 100 400mm Price and Availability:
The official UK price is approximately £4,400, US price is approximately $4,299.99 and Euro price is approximately €5,000. The product will be available in June 2026. Please keep an eye on their website for more details.
