Sony FE 100-400mm f/4.5 GM OSS Is Official — Constant Aperture, 3x Faster AF, $4,298

Key Takeaways

• Sony officially announced the FE 100-400mm F4.5 GM OSS on May 13, 2026, alongside the a7R VI — confirming what leaked late in April. The new G Master super-telephoto carries a constant f/4.5 aperture across the full zoom range, replacing the variable-aperture f/4.5-5.6 GM from 2017.
• Autofocus is up to 3x faster than the predecessor and subject tracking is approximately 50% improved, driven by four custom XD Linear Motors and Sony’s latest AF algorithms. It is fully compatible with Alpha 9 III’s 120fps continuous shooting with full AF/AE tracking.
• MSRP is $4,298 (Sony lists $4,299.99 USD). Pre-orders are open at B&H and authorized Sony retailers; shipping begins June 2026. The lens pairs naturally with the simultaneously-launched a7R VI ($4,499) for wildlife, birding, and sports photographers.
• Weight is 1,840 g (65 oz / 4.06 lbs) with an inner-zoom magnesium-alloy build. Optical formula uses one ED XA, two XA, two Super ED, and three ED elements with Nano AR Coating II. Compatible with Sony’s 1.4x and 2x teleconverters for reach up to 800mm or 1,200mm in APS-C mode.

What leaked in late April is now real. Sony officially announced the FE 100-400mm F4.5 GM OSS on May 13, 2026 — the same day the a7R VI body landed. The new G Master super-telephoto is the successor to Sony’s eight-year-old FE 100-400mm f/4.5-5.6 GM OSS, and it brings the single most-requested change to that lens: a constant f/4.5 aperture across the entire zoom range.

The price lands at $4,298 (Sony’s official spec sheet lists $4,299.99 USD), with pre-orders open now and shipping expected to begin in June. That puts it roughly $1,500 above the predecessor’s current $2,698 street price — meaningful, but well below comparable competitor offerings like Nikon’s $12,400 AF-S 180-400mm f/4E TC. For wildlife, birding, and sports photographers on Sony E-mount, this is the lens that closes the most-cited gap in the GM telephoto lineup. Pre-order watch on Amazon →

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Constant f/4.5 — The Headline Change

The original FE 100-400mm GM was an f/4.5-5.6, meaning the maximum aperture darkened by 2/3 of a stop as you zoomed in. That is normal behavior for variable-aperture super-telephotos, and most photographers worked around it. But it forced exposure compensation while zooming, complicated manual exposure on fast-moving subjects, and lost light at the focal length where you needed it most — the long end, where you’re typically working at high shutter speeds to freeze action.

A constant f/4.5 fixes all of that. No exposure shift across the zoom range, full 2/3-stop more light at 400mm, and the resulting flexibility with teleconverters changes meaningfully — a 1.4x TC turns the lens into a 140-560mm f/6.3 (still autofocus-viable on modern Sony bodies), and the 2x TC reaches 200-800mm at f/9. With the APS-C crop mode on bodies like the a7R VI or a9 III, that becomes 300-1,200mm equivalent — territory that previously required a separate $13,000 prime.

3x Faster Autofocus, 120fps Compatible

Sony’s spec claim is “up to 3x faster AF” versus the predecessor, with “approximately 50% improved subject tracking.” Those numbers come from four newly-developed XD (extreme dynamic) Linear Motors driving a floating focus mechanism, paired with the latest generation of Sony’s tracking algorithms. The lens is fully compatible with the Alpha 9 III’s signature 120fps continuous shooting at full AF/AE tracking — a combination only a handful of telephoto lenses on any mount currently support.

Real-world AF performance on telephoto lenses is dominated by two things: how fast the focus group can physically move, and how accurately the camera can drive it. The XD Linear Motor design specifically addresses the first half — XD motors are what Sony uses in its fastest-focusing primes (the 600mm f/4 GM and 400mm f/2.8 GM). Putting four of them in a zoom is unusual; most variable-aperture telephoto zooms use one or two ring USM-style motors and accept slower AF as a tradeoff for cost and weight. Sony is explicitly not making that tradeoff here.

The a7R VI Pairing

Sony’s decision to launch this lens on the same day as the a7R VI is not a coincidence. The two products are designed as a system. The a7R VI’s 66.8MP stacked sensor delivers per-pixel detail that makes the new GM’s optical formula meaningfully different from the predecessor — the older lens was sharp enough for the 61MP a7R V, but the a7R VI’s stacked readout combined with the AI-powered AF stack from the a1 II creates a body the older variable-aperture optics genuinely couldn’t fully resolve at the long end.

For wildlife and birding photographers, this is the new reference combo: $4,499 body plus $4,298 lens = $8,797 for a system that competes head-on with Nikon’s Z9 + 180-600mm f/5.6-6.3 ($5,500 + $1,697 = $7,197) and Canon’s R5 II + RF 100-500mm ($4,299 + $2,699 = $6,998). Sony’s package is more expensive on paper, but the constant f/4.5 aperture and 120fps AF/AE tracking on the a9 III are differentiators neither Nikon nor Canon currently match at any price point. For sports photojournalists who need the sideline reach and decisive-moment frame rate, the Sony stack is now the most capable mirrorless option on the market.

Who Should Actually Buy It

This lens is straightforwardly the right call for wildlife photographers on Sony E-mount who currently own the variable-aperture FE 100-400 GM and want better low-light performance at the long end without giving up the zoom flexibility for a prime. It is also the right call for sports photojournalists who shoot at indoor venues or stadium twilight where the extra 2/3 stop matters. And it makes sense for any a9 III owner who wants the only zoom currently optimized for the 120fps shooting workflow.

It is the wrong call for casual telephoto shooters who don’t need constant aperture, can live with f/5.6 at 400mm, and would rather put $1,500 toward a body upgrade or a second prime. The existing FE 100-400mm f/4.5-5.6 GM OSS is still an excellent lens at $2,698, and Sony has given no indication of discontinuing it. For people who are not specifically choosing this lens for the constant aperture or the AF speed, the older version is still in the lineup and still the better value.

Frequently Asked Questions

When does the new Sony 100-400mm GM actually ship?

Sony lists “available in June 2026” on the official spec sheet. Pre-orders are open now at B&H, Sony’s direct store, and authorized retailers. Expect units to start arriving in customer hands during the first two weeks of June assuming no supply-chain issues.

Does it work with Sony’s 1.4x and 2x teleconverters?

Yes. The lens is fully compatible with Sony’s SEL14TC (1.4x) and SEL20TC (2x). With the 1.4x: 140-560mm f/6.3. With the 2x: 200-800mm f/9. On APS-C crop mode (a7R VI, a9 III, a6700): up to 1,200mm equivalent reach. Autofocus remains active on current Alpha bodies with both teleconverters.

Is the constant f/4.5 worth $1,500 over the older variable-aperture version?

For working professionals shooting wildlife or sports — yes, comfortably. The exposure-shift fix alone saves frames in fast-changing light, and the AF speed upgrade is a quality-of-life change that compounds over thousands of shutter actuations. For enthusiasts who shoot mostly at 100-200mm or who don’t routinely fight light at 400mm, the older lens at $2,698 is still excellent value and the upgrade is harder to justify.

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Image credit: editorial composition by PhotoWorkout. Spec details credit to Sony’s official Alpha Universe announcement, Imaging Resource, and Photography Life — all sources cited below.

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