Opinion: enough with claiming the world's fastest autofocus

[sincity]

As helpful as it is to have camera manufacturers focusing on something other than megapixels these days, they still need to come up with reasons to brag about their latest models; whether it's a brand-new feature or an existing one made much better, new cameras need a reason to exist.

Today, the focus seems to be on focus itself – more specifically, just how promptly an autofocus system can spring to life and get a lock on the subject you’re shooting. What we now see is a suspiciously high number of cameras with the words 'world’s fastest autofocus system' somewhere in their press release. 

Unless you’re blessed with the reflexes of a fly, autofocus speed is incredibly difficult to measure in real-world conditions, so we’re taking the manufacturers at their word when they claim their latest camera can manage to focus in 0.04 or 0.03 seconds. But when everyone starts to claim what appears to be same crown for their own system, you start to wonder what’s going on – and how exactly they can do this.

The caveat

Scan a new camera’s press release and you’ll notice that claims about the world’s fastest anything are almost always accompanied by an asterisk, dagger, or a superscripted number, as there are a number of party tricks that need clarification. Whichever it is, the reason for its inclusion is the same: whatever it is that's being claimed is only true in very specific conditions. 

Take Canon’s latest EOS RP mirrorless camera. The very first paragraph of the press release claims it has the world’s fastest autofocus, but you have to work your way to the small print right at the end to understand exactly what Canon means by this. It reads (take deep breath):

As of 13 February 2019, among interchangeable lens digital mirrorless cameras incorporating a 35mm full frame equivalent image sensor with contrast detection AF and phase detection AF on the image plane. Calculated from the results of measured AF speed, based on CIPA guidelines (differs depending on shooting conditions and lens used). Measured using internal methods. Measurement conditions: EV12 (ambient temperature/ISO 100), Manual Mode, using the RF24-105mm F4 L IS USM (at a focal length of 24mm) with the following settings: shutter released using the shutter button, 1-point AF (Center AF), One-Shot AF.

So, it's with a specific lens that few people own, used at a specific focal length, with a specific method of focusing and in a specific focus mode. Canon deserves credit for transparency, but “measured using internal methods” means nothing if you don’t know what those methods are. Furthermore, the fact that it’s only relevant against “digital mirrorless cameras incorporating a 35mm full frame equivalent image sensor with contrast detection AF and phase detection AF on the image plane”, may well be as clear as it is fair, but these models still only represent a fraction of the camera market as a whole.

Everyone seems to be at it

The EOS RP is just the most recent example – similar claims were made for the previous EOS R and the company's DSLRs before this – but Canon isn’t the only manufacturer playing this game. Indeed, you don’t need to look too far back to find many other brand's claiming the world’s fastest autofocus for their own models, with each claim coming with the obligatory caveats. 

This includes Sony, with its A6400 earlier this year, and previously with its RX100 IV and RX100 V compact cameras, along with Panasonic with its Lumix G9. Fujifilm, Olympus and Nikon have all marketed cameras with similar claims in the past.

Few people will read the small print to understand exactly what’s being stated, but these claims are often repeated elsewhere without qualification, which makes them even less accurate or useful. Of course, manufacturers can’t be held responsible for that, but the intention is to get that headline claim out there, and assume you won't do any research beyond this. 

We’re also now at a point where a measured difference of 0.01 second between two models makes virtually no difference in practice, even less so if these speeds are only realized in very specific circumstances. When you consider the myriad other factors that inform the capabilities and performance of different autofocus systems – be they tangible ones such as the extent to which an AF system covers the frame, or things that can only be understood through testing – you see just how little value there is in such a simplistic statement.

Such claims will always attract attention, though – and that, of course, is the point. And cameras do get better over time, partly through having sprightlier and more refined autofocusing systems, so we should expect the same kinds of claims to keeping being made. But if you genuinely want to buy the camera with the 'best' autofocusing then it makes far more sense to focus on the technical details, and figure out what your particularly strand of shooting requires. How well a camera adheres to a moving subject; or acquires a lock in poor light or with low-contrast subjects; or gives you agency over adjusting how a focusing system responds to changes in a subject’s movement – it’s the sum of all these things that separate good autofocusing systems from great ones.

• How to master manual focus

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