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Sony FE 100-400mm f/4.5 GM OSS: Constant Aperture, Inner Zoom, and 3× Faster AF
Announced alongside the a7R VI, Sony's new FE 100-400mm f/4.5 GM OSS replaces the variable-aperture f/4.5-5.6 model with a constant f/4.5 aperture across the full zoom range. The lens uses an inner-zoom design, four XD Linear Motors, and promises autofocus up to three times faster and tracking up to 50 percent more accurate than its predecessor.
Overview
Sony announced the FE 100-400mm f/4.5 GM OSS on May 13, 2026, alongside the a7R VI. The lens is a full replacement for the FE 100-400mm f/4.5-5.6 GM OSS, which launched in 2017 and became one of the most popular telephoto zooms in the E-mount ecosystem.
The most significant change is the adoption of a constant f/4.5 aperture across the entire zoom range. The original lens was two-thirds of a stop slower at 400mm (f/5.6) — a meaningful difference in available light and depth of field control at maximum telephoto reach.
Optical Design
The new lens uses an inner-zoom design, meaning the physical barrel length does not change as the photographer zooms from 100mm to 400mm. This reduces handling imbalance when zooming, makes weather sealing more straightforward, and removes the risk of the lens "pumping" air during zoom changes in dusty conditions.
Maximum magnification is 0.25×, which Sony says is suitable for close-focus wildlife and environmental shots without a separate macro lens. Optical image stabilization (OSS) is built in and works cooperatively with the in-body stabilization of compatible Sony bodies.
Autofocus
The lens uses four XD (extreme dynamic) Linear Motors — one more than the original — to drive the focus groups. Sony claims autofocus speed up to three times faster than the predecessor and subject tracking accuracy up to 50 percent better.
These figures are measured against the 2017 lens, which used an older linear motor design. In practice, the combination of the new lens and the a7R VI's Real-time Recognition AF+ system should deliver substantially improved hit rates on erratic subjects like birds in flight.
Handling
The lens includes a detachable, rotatable tripod collar compatible with Arca-Swiss plates. Three focus hold buttons are distributed around the barrel. A physical aperture ring and a dedicated zoom lock switch are both present.
Weight and exact dimensions have not been released at launch. Sony has stated the lens is weather-sealed to the same standard as the a7R VI body.
Price and Availability
The Sony FE 100-400mm f/4.5 GM OSS is priced at $4,299.99 in the United States and $5,599.99 in Canada. It is scheduled to begin shipping in early June 2026.