The RX100 V gains a 315-point phase detection autofocus system, which is a first on any 1"-sensor compact that's ever been released (or shipped, anyway). You may not notice a huge change when shooting stills in Single AF, but it makes a noticeable difference when shooting with continuous autofocus. No more hunting or 'CDAF wobble'. Initial acquisition speed is blazing fast in the auto 'Wide' AF area mode. The system can keep up with your subject even if you're at the full 24fps burst speed. Of course, this is so long as you've had the camera successfully lock onto your subject, or are following the subject yourself with 'Center' or 'Flexible Spot' modes. Thankfully, it's pretty easy to follow your subject since you're viewing a 24 fps, movie-esque feed during bursts.

The RX100 V's AF system covers 65% of the frame with 315 points.

AF options

The RX100 V's AF system is, in terms of options, identical to its predecessor. There are five different focus area modes:

  • Wide - this setting analyzes the full scene in front of you and will automatically choose where to initiate focus. It prioritizes faces when face detection is on.
  • Center - This setting uses a box in the center of the frame to focus.
  • Flexible Spot - this allows you to use a box of three preset sizes that you can manually move around the screen to choose your point of focus. You can place it in the center of the frame, obviously, rendering the 'Center' area mode redundant.
  • Expand Flexible Spot - this mode uses a central AF point, and utilizes surrounding 'helper' points to maintain focus on your intended subject. You can move this cluster around the frame, like you can in Flexible Spot.
  • Lock-on AF - This can only be used in continuous AF mode and offers all the other autofocus area modes as sub-options. This can be very confusing, and occasionally, redundant.
Because of the complex and confusing nature of the system of the system and the deep-ish depth of field offered by the sensor size, I generally just left the RX100 V in 'Center' or 'Flexible Spot' and recomposed if necessary. 70mm equiv., ISO 125, 1/160 sec, F3.5. Photo by Carey Rose

Some area modes, like Wide, behave exactly the same whether you choose it under the 'Lock-on' sub-menu, or just choose it on its own. Others, such as 'Flexible Spot,' behave very differently - under Lock-on, it will attempt to identify a subject to track around the frame, but if you select it on its own (not Lock-on), it behaves more or less like single-point continuous AF.

Here's a hint to Sony: get rid of 'Center' which is just a special case of 'Flexible Spot', and get rid of all different sizes of Flexible Spot under 'Lock-on AF', since it tends to ignore your chosen setting anyway. Furthermore, it's confusing that 'Lock-on AF' has a 'Wide' option. Lock-on is used to specify a subject, whereas 'Wide' is used not to. We can't think of a single situation where one would want to use them together, as their intents are opposite. Clearing up some of these less useful AF modes would provide a better user experience, and faster selection of one's desired AF mode.

On top of all of this, there's Face Detection, which is turned on/off separately and can be assigned to the Fn menu. This will indicate any faces that the camera has detected in the scene but the camera will only focus on these faces if your chosen focus area mode overlaps with or is near the face (so an off-center face won't be prioritized over the subject in the middle of the frame, if you're in Center AF area mode, for instance). There's also an option to teach the camera specific faces, which it will then prioritize over unknown faces. You can even prioritize which faces it should prioritize over others. In real-world usage though, this isn't a terribly reliable way to tell the camera which person to focus on; we generally have better luck indicating which face we're interested in on-the-fly using Eye AF with the center point and recomposing in AF-C.

The RX100 V offers a four main AF area modes, then Lock-On (tracking) versions of those modes.

On top of these are the Face Detection/ Recognition options, an Eye AF mode and, presumably for video use, a separate Center Lock-On AF function.

It's worth learning how these interact with one another.

Eye AF is available in both single and continuous AF, even when shooting with continuous drive at 24 fps (it's really something to behold). To use this mode, you'll need to assign Eye AF to one of the camera's precious few custom buttons. In AF-S mode, it will highlight an eye for around 1 second as the eye is focused on. Eye AF is eminently more usable in AF-C mode, where pressing and holding your assigned Eye AF button will find and follow the eye nearest your selected AF point, or simply the nearest eye the camera can find in the scene in 'Wide' area mode. Frustratingly, Sony's Eye AF algorithm continues to ignore your initial subject if it loses it even for a split second. Eye AF does not require Face Detection to be engaged to work.

Vestigial 'Center Lock-on AF'

Just to add a further level of complexity, the camera still offers Center Lock-on AF as a separate function (not to be confused with the Lock-on AF Center AF area mode, with which it's incompatible). So far is we can tell, this is a vestigial feature that dates back to before Sony got the far more usable Lock-on AF area mode (triggered with a simple half-press of the shutter button) worked out. The Center Lock-on AF function is locked onto a subject by pressing the central button on the back of the camera and presumably remains in the camera because it's the only tracking AF mode available while in movie mode - which is something we really wish would change. There's no reason for Lock-on AF area mode to be unavailable in video, and it's particularly a shame because of how user-unfriendly Center Lock-on AF is: you'll have to either assign it to a custom button or Fn menu, then turn it on, then press the center back button to initiate subject tracking.

The phase detection difference - or lack thereof

As with other Sony cameras with phase detection, the RX100 V uses a hybrid approach to autofocus when in AF-S (single AF) mode. This means there's a focus 'hunt' (which is still quite rapid), as the camera uses phase detection followed by contrast detection to ensure accurate focus.

However, when in AF-C and certain area modes, AF can be nigh instantaneous, indicating that, unless the camera fails to find focus right away, the contrast-detect 'hunt' is skipped, prioritizing the phase detection data from the new system. Given the accuracy of Sony's on-sensor phase-detect system, we wonder why Sony doesn't skip the contrast step in AF-S as well.

The near-instant acquisition of this subject in Wide mode made it far more practical than any of the Lock-on modes, whose acquisition time can be sluggish and / or finicky. Straight-out-of-camera JPEG at 70mm equiv., ISO 500, 1/250 sec, F2.8. Photo by Carey Rose

Unfortunately, the phase detection system has not helped the dependability of acquiring a subject in Lock-on AF in continuous autofocus. Often, we simply had better luck leaving the camera on 'Wide' and allowing it to choose a subject to track - which it does nearly instantaneously. When we tried to use the Lock-on: Center or Lock-on: Flexible Spot AF areas, the camera would often result in a lag before initiating tracking, presumably because object recognition is trying to figure out what it is in your AF area it's meant to track. More often than we'd like, Lock-on even ignored the subject under our AF point, immediately jumping off to another subject somewhere else in the frame.

To put this in perspective, Canon's iTR is often just as unreliable tracking subjects in complex scenes, but that's our point: like iTR, once you drop below a threshold of reliability, you just don't use it. With the image sensor available for object recognition, we expect better subject tracking - perhaps on par with the camera's own Eye AF tracking ability or, ideally, something as good as Nikon's 3D tracking.

Despite this, as stated earlier on this page, once you do get the camera to start tracking your subject, it does so very well - even when shooting at 24fps. That's no small feat for a pocket camera. Let's take a look at how well it did in our standard bike test, and some real-world low light tests on the next page.