Sony FE 100-400mm F4.5 GM OSS

A faster G Master telephoto zoom for the moments that don’t wait.

The Sony FE 100-400mm F4.5 GM OSS brings a major performance leap to Sony’s professional telephoto zoom lineup, pairing a versatile 100-400mm focal range with a constant f/4.5 maximum aperture, internal zoom design, Optical SteadyShot stabilization, and faster autofocus built for wildlife, birding, sports, and photojournalism.

Compared to the FE 100-400mm F4.5-5.6 GM OSS, the new lens is designed for photographers who want more speed, more consistent exposure through the zoom range, stronger subject-tracking performance, and a more stable handling experience when working handheld or on the sidelines. Sony states that autofocus is up to approximately 3x faster, with approximately 50% improved subject tracking when mounted on the Alpha 9 III under Sony test conditions.

Looking Glass Photo’s Take:

The big story here is not simply that Sony made a new 100-400mm lens. It is that Sony made a constant f/4.5 G Master 100-400mm with internal zoom and significantly faster autofocus. That changes the character of the lens.

The original FE 100-400mm F4.5-5.6 GM OSS has been a trusted choice for wildlife, sports, travel, and outdoor photography because it offers excellent reach in a relatively manageable package. The new FE 100-400mm F4.5 GM OSS is more ambitious. It is larger, heavier, and more expensive, but it gives photographers a brighter long-end aperture, steadier balance while zooming, faster AF performance, and more professional control in the field.

For casual travel or hiking, the older 100-400mm may still make more sense. For serious birding, wildlife, field sports, motorsports, outdoor events, and high-end Sony Alpha work, the new f/4.5 version is the one built to keep up with faster cameras and more demanding subjects.

Why photographers will like the Sony FE 100-400mm F4.5 GM OSS

• Constant f/4.5 aperture throughout the zoom range — Maintains the same maximum aperture from 100mm to 400mm, helping avoid exposure shifts while zooming.
• G Master optical design — Uses a newly developed ED XA element, one XA element, two Super ED elements, and three ED glass elements to help control chromatic and spherical aberrations across the zoom range.
• Fast autofocus for action — Four custom-optimized XD Linear Motors, a floating focus mechanism, and updated AF algorithms deliver autofocus speeds up to approximately 3x faster than the FE 100-400mm F4.5-5.6 GM OSS under Sony test conditions.
• Improved subject tracking — Sony states approximately 50% improved subject tracking compared with the previous 100-400mm GM when mounted on the Alpha 9 III.
• Internal zoom design — The lens maintains a constant length and stable center of gravity throughout the zoom range, making it easier to track fast subjects and keep framing steady.
• Optical SteadyShot stabilization — Built-in stabilization supports Active Mode and coordinated stabilization control with compatible camera bodies.
• Professional field controls — Four focus hold buttons and a dedicated function ring give photographers more ways to customize operation while shooting.
• Teleconverter compatibility — Compatible with Sony’s 1.4x and 2x teleconverters, giving photographers the ability to reach up to 800mm, or up to 1200mm equivalent in APS-C mode with the 2x teleconverter.
• Built for outdoor work — Dust- and moisture-resistant design, plus a fluorine coating on the front element, helps the lens hold up in challenging field conditions. Sony notes the lens is not completely sealed against dust or water droplets.

Ideal for

Wildlife photographers, bird photographers, sports photographers, outdoor event shooters, photojournalists, and Sony Alpha users who want a professional 100-400mm zoom with faster autofocus, constant f/4.5 exposure, and stable internal-zoom handling.