Sony is refining its professional optics lineup with the introduction of the Sony FE 100-400mm f/4.5 GM OSS, a telephoto zoom lens specifically engineered for the demanding environments of wildlife photography, sports, and photojournalism. The new lens represents a strategic shift in the G Master series, prioritizing constant light transmission and physical stability over the compact, variable-aperture design of its predecessor.
While most updated lenses in Sony’s high-end ecosystem carry a “Mark II” designation, this model breaks tradition by omitting the moniker. Despite the naming convention, the lens serves as a substantial evolution of the previous 100-400mm f/4.5-5.6 GM OSS, introducing a constant aperture and a redesigned physical chassis that alters how the lens handles both light and balance.
The transition to a constant f/4.5 aperture is the most critical upgrade for working professionals. By maintaining this aperture across the entire zoom range, the lens is two-thirds of a stop faster at the 400mm end than the previous version. This improvement allows for better subject separation and increased light-gathering capabilities, which are essential when shooting in the fading light of a sideline or the dense canopy of a forest.
A Shift in Physical Architecture
Beyond the optics, Sony has overhauled the mechanical design of the lens. The new model features an inner-zoom system, meaning the lens barrel does not extend as the photographer zooms from 100mm to 400mm. This is a significant departure from the older 100-400mm f/4.5-5.6 GM OSS, which physically lengthened during operation.
For photographers using gimbals or heavy tripods, an inner-zoom design is a major ergonomic advantage. It prevents the center of gravity from shifting forward during a zoom, maintaining the balance of the camera rig and reducing the need for constant tripod adjustments during fast-paced action.
However, these professional enhancements come with a physical cost. The move to a constant aperture and internal zooming has increased the lens’s footprint. The Sony FE 100-400mm f/4.5 GM OSS weighs 1,840 grams (4.06 pounds), a notable increase from the 1,495 grams (3.3 pounds) of the previous model. It also features a wider diameter of 119.8 millimeters, compared to the 93.9 millimeters of its predecessor.
Optical Precision and Bokeh Control
To maintain high resolution across the entire focal range, Sony has integrated a complex array of specialized glass. The optical formula includes two Super ED elements, one XA lens, and three standard ED glass pieces. The centerpiece of this system is a new ED XA (extra-low dispersion extreme) element, designed to suppress chromatic aberrations while minimizing “onion-ring” bokeh—the concentric circles that can sometimes appear in out-of-focus areas.
The lens also utilizes Nano AR Coating II to reduce flare and ghosting. To further refine the aesthetic quality of the images, Sony increased the aperture blade count to 11, providing a more circular opening than the 9 blades found in the previous version, resulting in smoother background blur.
The autofocus system has seen a similar leap in performance. Equipped with four G Master XD Linear Motors, the lens offers faster responsiveness and more precise tracking. According to Sony, autofocus speed is up to three times faster, while subject tracking has improved by up to 50 percent.
| Feature | FE 100-400mm f/4.5-5.6 GM | FE 100-400mm f/4.5 GM |
|---|---|---|
| Maximum Aperture | f/4.5 – 5.6 (Variable) | f/4.5 (Constant) |
| Zoom Mechanism | Extending | Inner-zoom |
| Weight | 1,495g | 1,840g |
| AF Motors | Standard Linear | 4 XD Linear Motors |
| Aperture Blades | 9 | 11 |
Professional Utility and Integration
The lens is built for the rigors of field work, featuring dust- and moisture-resistant construction. For those needing additional reach, it is compatible with Sony’s 1.4x and 2x teleconverters. When paired with these accessories, the lens transforms into either a 140-560mm f/6.3 or a 200-800mm f/9, extending its utility for extreme wildlife distances.
On the chassis, Sony has included a suite of professional controls, including four Focus Hold buttons and a rotating tripod collar with selectable clicking. An assignable function ring allows users to quickly toggle between APS-C cropping or shift focus between the close range and infinity. The lens also includes a security slot and a drop-in filter holder for specialized lighting or polarization needs.
One area where the new lens takes a slight step back is close-focusing. It can focus as close as 0.64 meters (2.1 feet) at 100mm and 1.5 meters (4.9 feet) at 400mm, yielding a maximum magnification of 0.25x. This is slightly less than the 0.35x magnification offered by the older, variable-aperture model.
Pricing and Market Availability
The Sony FE 100-400mm f/4.5 GM OSS is positioned as a premium tool for the professional market. It will begin shipping in early June with a U.S. Price of $4,299.99 and a Canadian price of $5,599.99. This represents a $1,500 increase over the original 100-400mm f/4.5-5.6 GM OSS in the U.S. Market.
This pricing reflects the shift from a “prosumer” telephoto zoom to a dedicated professional instrument, aligning it more closely with the performance standards of the Sony E-mount ecosystem’s top-tier lenses.
Sony is expected to provide further firmware updates and compatibility details as the lens reaches retail shelves in June. Those interested in the latest professional optics can find official updates on Sony’s corporate newsroom.
Do you think the move to a constant aperture justifies the weight and price increase? Share your thoughts in the comments or share this story with your fellow photographers.
