Both weigh under a kilogram — 994g and 995g (both 2.2 lbs) respectively, excluding the tripod foot — and share the same 108mm barrel diameter. They’re so close in size and feel that it’s easy to pick up one thinking you’ve grabbed the other. Sony claims both are the lightest super-telephoto primes in their class, and the numbers bear that out.

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Sony provided both lenses to us ahead of the announcement, and we’ve been using them for a couple of weeks. In this article, we’ll walk you through the key areas of their designs.

Optics

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Optically, the lenses are very similar. The 400mm comprises 22 elements in 16 groups, and the 600mm uses 24 elements in 17 groups. Both share the same core glass: three Super ED elements and one ED element. According to Sony, the shared Super ED elements are what keep chromatic aberration in check across both focal lengths.

In fact, the optical designs are so similar – the 600mm adds two elements and substitutes a third – that it can almost be thought of as a 400mm lens with a built-in teleconverter. The minimum focus distance is identical at 2.5m, but the aperture isn’t quite proportional: a true 1.5x converter would make F4.5 become F6.75, whereas the 600mm manages to achieve F6.3, so it’s close to the idea without being a literal case of it.

Both lenses feature a single front lens element design, rather than a multi-element front group, which Sony credits for pushing the center of gravity back toward the camera body for better balance, and both include an 11-blade circular aperture, which it claims will help render more natural bokeh (check out our sample galleries below for real-world examples).

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The two lenses also work with Sony’s SEL14TC 1.4x and SEL20TC 2.0x teleconverters. The 400mm extends to 560mm F6.3 or 800mm F9; the 600mm goes to 840mm F9 or 1200mm F13. The 600mm’s maximum magnification of 0.25x also nudges ahead of the 400mm’s 0.18x, despite both sharing a 2.5m (8.2 ft) minimum focus distance.

Autofocus

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Each lens uses two XD (extreme dynamic) linear motors, one driving each focus group. Sony claims both can maintain focus tracking at up to 120 fps on the a9 III and support subject tracking during 4K 120p video recording.

We used the lenses with a Sony a7 V body, so we weren’t able to put the 120 fps tracking to the test, but the camera maintained tracking at its maximum 30 fps burst rate.

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Autofocus is quick and snappy. The only moment it felt sluggish was when switching from a subject very close up to one very far away, which isn’t unusual for a super-telephoto, and exactly the scenario the focus limiter is designed for – we’ll get to that in a moment.

Sony’s subject detection worked well with both lenses. Whether tracking a bird or a large mammal, the system tracked subjects like glue, and only in rare cases would one of the lenses fall behind in maintaining focus.

On-lens controls

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Both lenses include an AF/MF switch, a full-time DMF (direct manual focus) ON/OFF switch, a focus range limiter with two settings (full range and ∞–7m), an OSS ON/OFF switch and an OSS mode switch.

The lenses support three stabilization modes: Mode 1 for normal camera shake, Mode 2 for panning, and Mode 3, which Sony says minimizes framing disturbance for fast or irregularly moving subjects. I confess that I didn’t think about what OSS mode the lenses were in when shooting subjects like birds, leaving them in Mode 1, which seemed to work fine, though it’s possible a more experienced bird photographer would notice the difference.

The limiter’s ∞–7m setting keeps the AF system from hunting through closer distances; it proved particularly useful when photographing an animal through grass or foliage between me and the subject, ignoring close-in distractions so the AF system could lock on to what I actually intended.

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Four focus hold buttons are distributed around the barrel on both lenses, and all are customizable. A function ring sits just behind them and can be assigned a range of camera settings.

The manual focus ring is nice and deep, giving plenty of surface to grip and turn. Both lenses support full-time DMF, so there’s no mode-switching required to take over focusing mid-shot. In fact, I ran into several shooting situations where a quick twist of the focus ring to bring a partly obscured subject into focus was the fastest way to get the camera’s subject detection system to lock onto a subject, like a bird, which it then began tracking.

Design and build

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Both lenses are effectively the same size, sharing a 108mm barrel diameter and a 95mm front filter thread. Where they differ by a small amount is in length: the 400mm measures 242mm; the 600mm is 263mm — a difference of just 21mm.

Sony claims dust and moisture resistance through sealed seams, silicone rubber gaskets around buttons and switches, a sealed lens mount ring and a fluorine-coated front element. In my own use, the 400mm held up to one very wet day of shooting with steady rain for about 3 hours. The lens was visibly wet on the outside and showed no signs of water reaching the interior. It wasn’t a controlled test, but that anecdotal experience lends credence to Sony’s claims.

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The tripod foot is removable on both, using a twist-lock mechanism that makes attaching or removing it quick and easy. A soft carrying case is included with each lens, and it’s one thing that felt a little bit wanting; it feels like a one-size-fits-all case designed to accommodate larger lenses, leaving a fair amount of room for the lenses to move around inside.

The one thing that really stands out when using both lenses is how little weight sits toward the front. The balance point falls well back toward the camera, which makes handholding for extended periods more comfortable than the physical size might suggest.

Lightest in class

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Sony claims both lenses are the lightest super-telephoto primes in their class. The natural comparison is Nikon’s Z 400mm F4.5 VR S and Z 600mm F6.3 VR S, which tip the scales at 1160g (2.6 lbs) and 1390g (3.1 lbs), respectively, both excluding the tripod collar. That makes the Sony 400mm around 14% lighter than its Nikon counterpart and the 600mm roughly 28% lighter, which is a meaningful gap at the 600mm end.

Nikon’s lenses have been well received, so it’s easy to see why Sony would want equivalents in its own lineup. But Sony isn’t competing only on weight: Nikon’s 400mm F4.5 sells for around $3,500 while its 600mm F6.3 sells for $5,200, so Sony is undercutting Nikon on price as well. For photographers already invested in Nikon, that’s unlikely to justify a system change once bodies, accessories and the other complications of switching are accounted for, but for Sony shooters, or anyone who hasn’t fully committed to a system, the options look very different than they did a week ago.

Compared to Sony’s faster 400mm and 600mm primes

Sony already makes faster primes at both focal lengths: the FE 400mm F2.8 GM OSS and the FE 600mm F4 GM OSS, which offer roughly a 1.3-stop aperture advantage over the new models, and retail for much higher prices, around $12,000 and $13,000, respectively.

The weight savings of the new lenses — not to mention the cost — are substantial in both cases. They represent a trade-off: faster aperture vs. a lightweight, more mobile design. Those who need to capture photos in any setting with fast shutter speeds, like indoor sports (think: gymnastics), have a real reason to favor Sony’s F2.8 and F4 primes. But if you can trade one and a third stops for a lens that comes in under a kilogram and fits in your daypack, the new 400mm and 600mm GM lenses make a clear case.

Sample galleries

We expect one of the most common applications for both new lenses to be wildlife photography, so we’ve primarily built our sample galleries around this use case. Most of the photos you see in these galleries were shot at Ninepipe National Wildlife Refuge in Montana, the Confederated Salish and Kootenai Tribes Bison Range in Montana, and at the Oregon Zoo.

Please do not reproduce any of these images on a website or any newsletter/magazine without prior permission (see our copyright page). We make the originals available for private users to download to their own machines for personal examination or printing; we do so in good faith, so please don’t abuse it.