If you’ve ever reviewed footage from a shoot and noticed that unsettling in-and-out focus breathing pulsing through your clips, you’ll know how frustrating it is. The shot felt fine on the day. The subject was sharp. But that subtle, rhythmic pulse quietly ruining an otherwise solid take.
I’ve been there. And rather than just accepting it as “one of those things,” I wanted to actually test it.
Specifically, I wanted to know: is the camera body the problem, the lens, or a combination of both?
The Test.
I ran six of my most-used Sony full-frame E-mount lenses across two camera bodies, the Sony A7III and the Sony A9III, to see how the autofocus algorithm and the lens itself each contribute to focus pulsing and what I’m calling focus stepping (that hard, jerky shift you get when a subject makes extreme movements towards or away from the lens).
The lenses in the lineup:
- Sony Vario-Tessar T* FE 16–35mm F4 ZA OSS.
- Sony FE 24mm F1.4 GM.
- Sony Sonnar T* FE 55mm F1.8 ZA.
- Sony FE 85mm F1.8.
- Tamron 28–75mm f/2.8 Di III VXD G2.
- Sigma 24–105mm f/4 DG OS HSM Art.
The Results.
Tamron 28–75mm f/2.8 Di III VXD G2.
The clear winner, and perhaps the most surprising result of the whole test. On the A9III, focus pulsing was minimal, a non-issue to my eye, and even during extreme subject movement, the focus stepping felt smooth and controlled. On the older A7III, it still held up impressively well. Pulsing remained minimal, and while the focus stepping wasn’t quite as fast or accurate as on the A9III, it still felt smooth. For a third-party lens, that’s a genuinely strong result on both bodies.
Sigma 24–105mm f/4 DG OS HSM Art.
On the A9III, focus pulsing was very minimal, comparable to the Tamron. The focus stepping during extreme movements is noticeable though, which is worth flagging. Paired with the A7III, the pulsing does creep in, appearing every couple of seconds rather than constantly. That intermittent quality actually makes it harder to work with in some ways, it’s unpredictable enough that I wouldn’t want to rely on it during a live shoot. Focus stepping was also pronounced on the A7III. It should be noted, this lens is an EF mount adapted to E mount.
Sony FE 85mm F1.8.
On the A9III, focus pulsing was limited, though if your subject is moving while speaking, you’ll notice a slight jerkiness. The focus stepping during extreme movements was pretty hard and abrupt. On the A7III, the pulsing got noticeably worse, even with minimal subject movement. Interestingly, the focus stepping felt smoother on the A7III, but only because the camera couldn’t keep up with the same extreme movements the A9III handled. Smoother, but for the wrong reasons.
Sony Sonnar T FE 55mm F1.8 ZA.
On the A9III, focus pulsing was limited and even during extreme distance changes, focus felt largely smooth. On the A7III, it mirrored the 85mm, pretty bad pulsing, with focus stepping that felt smooth only because the speed and accuracy weren’t there to push it into difficult territory.
Sony FE 24mm F1.4 GM.
On the A9III, focus pulsing was limited, keeping in line with the other Sony primes. But the focus stepping during extreme distance movement was pretty bad and jerky which is worth noting if you’re shooting anything with significant subject movement. On the A7III, the pulsing was constant, in and out throughout, and the stepping was jerky too. Not ideal on either body if fast, accurate tracking matters.
Sony Vario-Tessar T FE 16–35mm F4 ZA OSS.
On the A9III, focus pulsing was very limited, continuing the trend. Stepping during extreme movement was still jerky. But on the A7III, which by this point in the test had been fairly unkind to most lenses, the focus breathing remained quite minimal, and the stepping was actually smooth. A small but genuine bright spot for A7III users.
What This Tells Us.
The camera body absolutely matters. The A9III’s autofocus algorithm does a meaningful job of reducing pulsing across the board, in most ways every lens performed better on it. But the lens is far from irrelevant. The Tamron in particular showed that third-party glass can outperform native Sony lenses in real-world autofocus behaviour, even on the older A7III body.
If you’re shooting on an older Sony Alpha like the A7III and autofocus performance is a priority, it’s genuinely worth considering third-party options like the Tamron 28–75mm f/2.8 Di III VXD G2 before assuming first-party Sony lenses will serve you better.
On newer bodies like the A9III, you’ve got more headroom, most lenses perform well enough that pulsing becomes less of a concern. That said, focus stepping during extreme movements is still a variable worth paying attention to depending on the lens.
I’d love to run this same test on the Sony A7V and the Sony FX3, both of which are on my radar as potential upgrades to the A7III. It would be genuinely useful to see how the same lenses translate across those bodies, and whether the pulsing issues improve when compared to the A7III with newer processing.
If you’ve done similar tests or have a lens you’d like to see included, let me know as I’m always curious to see how these results hold up across different setups.
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